System and method for controlling a vehicle

Abstract

A vehicle control system determines a non-zero upper limit for the deceleration of a vehicle to prevent the vehicle from rolling backward along a slope that the vehicle is currently traveling upward. The non-zero upper limit for the deceleration is determined by a controller based on a load carried by the vehicle, a speed of the vehicle, and a slope of a route that the vehicle is currently traveling. The controller is configured to monitor the deceleration of the vehicle and automatically prevent the deceleration of the vehicle from exceeding a non-zero upper limit by controlling the brakes and / or motor of the vehicle. The controller is also configured to activate the brakes and / or supply current to the motor of the vehicle when the vehicle is moving upward along a slope at a non-zero speed to prevent the vehicle from rolling backward.

Description

[0001] Divisional Application Instructions

[0002] This application is a divisional application based on the Chinese patent invention application with application number 201780081786.6, application date November 1, 2017, and invention name “System and method for controlling a vehicle”. Technical Field

[0003] Embodiments of the inventive subject matter described herein relate to vehicle control. Other embodiments relate to controlling a vehicle to prevent rolling back. Background Art

[0004] Vehicles such as off-highway mining vehicles "OHVs" and load-haul-dump vehicles "LHDs" used for mining and moving heavy loads from underground mines are well known. LHDs and other vehicles are typically commercially available in both diesel and electric versions, and often use electric wheels to propel or decelerate the vehicle in an energy-efficient manner. This efficiency is typically achieved by using a high horsepower diesel engine in combination with an alternator, a main traction inverter, and wheel drive assemblies mounted within the tires of the vehicle. The diesel engine is directly associated with the alternator so that the diesel engine drives the alternator. The alternator provides power to the main traction inverter, which provides electrical energy with a controlled voltage and frequency to the electric drive motors of the wheel drive assemblies. Each wheel drive assembly is mounted with a planetary gear transmission that converts the rotational energy of the associated drive motor into a high torque, low speed rotational energy output that is provided to the wheels.

[0005] In addition to providing power to the main traction inverter and thus to the electric drive motors to propel the vehicle, the alternator also provides power to hydraulic pumps and hydraulic motors used by various auxiliary vehicle systems such as for bucket movement and for application of service and parking brakes.

[0006] Due to the weight of these vehicles, the loads they carry, and the environments in which they are used, operating these vehicles on a grade may present some challenges, especially for inexperienced operators. Therefore, it may be desirable to provide a system and method for controlling a vehicle that is different from existing systems and methods. Summary of the invention

[0007] In one embodiment, a method for controlling a vehicle is provided. The method comprises the steps of controlling at least one traction motor of the vehicle to provide a controlled deceleration of the vehicle when traveling on a grade in a selected direction of travel, and automatically applying the service brakes of the vehicle when the vehicle is moving in the selected direction of travel.

[0008] In another embodiment, a system is provided. The system includes: a control unit configured to be electrically connected to a drive system of a vehicle, the drive system including at least one traction motor for providing a traction force to the vehicle; and a service brake associated with at least one wheel of the vehicle. In the absence of a command to provide a traction force in a selected direction of travel, the control unit is configured to automatically apply the service brake to prevent the vehicle from rolling backward when the vehicle moves in the selected direction of travel.

[0009] In one embodiment, a method for controlling a vehicle is provided, the method comprising the steps of determining a selected direction of travel of the vehicle, monitoring the direction of operation of a motor of the vehicle, monitoring the speed of the motor, and automatically applying the service brakes of the vehicle to prevent the vehicle from rolling backwards when a rolling backwards condition is detected.

[0010] In another embodiment, a system is provided. The system includes: a control unit configured to be electrically connected to a drive system of a vehicle, the drive system including at least one traction motor for providing a driving force to the vehicle; and a service brake associated with at least one wheel of the vehicle. The control unit is configured to automatically apply the service brake to prevent the vehicle from rolling backward when a rolling backward condition is detected.

[0011] In yet another embodiment, a vehicle is provided. The vehicle includes a drive system including a traction motor drivingly connected to a wheel of the vehicle, the motor configured to provide a motive force to propel the vehicle in a selected direction of travel in a propulsion mode of operation; a controller electrically connected to the drive system; and a friction brake associated with at least one wheel of the vehicle. The controller is configured to automatically engage the friction brake to prevent the vehicle from rolling backward when a rolling backward condition is detected.

[0012] In one embodiment, a control system for a vehicle (e.g., a brake control system) includes an electric drive system associated with at least a first set of wheels of the vehicle, and a drive system control unit configured to control the electric drive system to selectively provide electric power to at least the first set of wheels to propel the vehicle and electrically decelerate to slow the vehicle. The system also includes: a friction brake system associated with at least one of the first set of wheels or the second set of wheels of the vehicle; and a friction brake control unit configured to control the friction brake system for applying friction brakes to at least one of the first set of wheels or the second set of wheels. The drive system control unit is also configured to communicate with the friction brake control unit to control the amount of friction brake application during vehicle stopping and starting. For example, the drive system control unit may be configured to communicate with the friction brake control unit to at least partially automatically control the amount of friction brake application during vehicle stopping and starting on an inclined grade on which the vehicle is located.

[0013] In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electric power to at least the first set of wheels to propel the vehicle and electrically decelerate to slow the vehicle. The method also includes determining a torque level required for the vehicle to move up an inclined grade from a stop, and in response to input from an operator control for moving the vehicle up the grade, communicating with a friction brake control unit of the vehicle to remove friction brake application holding the vehicle stopped, while simultaneously controlling the electric drive system of the vehicle to provide electric power according to the determined torque level for moving the vehicle up the grade without significant vehicle rollback.

[0014] In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electric power to at least the first set of wheels to propel the vehicle and electrically decelerate to slow the vehicle. The method also includes determining a force required to hold the vehicle on an inclined grade on which the vehicle is positioned, and communicating with a friction brake control unit of the vehicle to reduce or increase an amount of friction brake application applied to at least one of the first set of wheels or the second set of wheels of the vehicle based on the force determined to hold the vehicle on the inclined grade.

[0015] In one embodiment, a vehicle control system includes a controller configured to determine a non-zero upper limit for vehicle deceleration. The controller is configured to determine the non-zero upper limit to prevent the vehicle from rolling backward along a slope that the vehicle is currently traveling upward. The non-zero upper limit for deceleration is determined by the controller based on a load carried by the vehicle, a speed of the vehicle, and a slope of a route that the vehicle is currently traveling. The controller is configured to monitor the deceleration of the vehicle and automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit by controlling the brakes and / or motors of the vehicle. The controller is also configured to activate the brakes and / or supply current to the motor of the vehicle to prevent the vehicle from rolling backward when the vehicle is currently moving upward along the slope at a non-zero speed.

[0016] In one embodiment, the method includes determining a non-zero upper limit for the deceleration of the vehicle to prevent the vehicle from rolling backward along the slope on which the vehicle is currently traveling upward. The non-zero upper limit for the deceleration is determined based on the load carried by the vehicle, the speed of the vehicle, and the slope of the route the vehicle is currently traveling. The method includes monitoring the deceleration of the vehicle and automatically preventing the deceleration of the vehicle from exceeding the non-zero upper limit by controlling the brakes and / or motor of the vehicle. When the vehicle moves upward along the slope at a non-zero speed, the deceleration of the vehicle is prevented from exceeding the non-zero upper limit by activating the brakes and / or supplying current to the motor of the vehicle to prevent the vehicle from rolling backward.

[0017] In one embodiment, a vehicle control system includes a controller configured to determine a selected travel direction of the vehicle, an operating direction of a motor of the vehicle, and an operating speed of the motor. The controller is configured to identify a backward roll condition of the vehicle in response to the operating direction of the motor of the vehicle being different from the selected travel direction of the vehicle. The controller is further configured to automatically slow or stop movement of the vehicle by automatically activating a brake of the vehicle in response to the backward roll condition being identified and the operating speed of the motor exceeding a specified non-zero speed threshold.

[0018] In one embodiment, a vehicle control system includes a controller configured to determine a lower limit for a vehicle speed. The controller is configured to determine the lower limit to prevent the vehicle from rolling backward along a slope that the vehicle is currently traveling upward. The lower limit is determined by the controller based on a load carried by the vehicle and the slope of the route that the vehicle is currently traveling. The controller is configured to monitor the speed of the vehicle and automatically prevent the vehicle speed from falling below the lower limit by activating the brakes of the vehicle. The controller is configured to activate the brakes based on the speed of the vehicle and independently of the acceleration of the vehicle. The controller is also configured to activate the brakes of the vehicle to prevent the vehicle from rolling backward when the vehicle is moving upward along the slope at a non-zero speed.

[0019] In one embodiment, a method includes receiving a throttle command representing an operator request to increase a throttle setting of the vehicle while brakes of the vehicle are engaged, increasing torque generated by one or more motors of the vehicle in response to receiving the throttle command, and releasing brakes of the vehicle in response to one or more of the torque generated by the one or more motors reaching a maximum available torque, the torque generated by the one or more motors reaching a target release acceleration, or expiration of a predetermined non-zero duration.

[0020] In one embodiment, the method includes determining whether the brakes of the vehicle have been released while the vehicle is in a stopped state on a grade of a route, in response to determining that the brakes have been released, allowing the vehicle to roll backward down the grade by no more than a specified non-zero threshold distance and / or rapidly accelerating the vehicle using torque generated by one or more motors of the vehicle, and smoothly transitioning the vehicle to movement up the grade by adjusting the torque generated by the one or more motors after allowing the vehicle to roll backward down the grade and / or rapidly accelerating the vehicle.

[0021] In one embodiment, the method includes repeatedly determining whether an operator input to release one or more brakes is received during a blanking interval (when one or more brakes of a vehicle in a stationary position on a grade) responsive to not receiving an operator input to release one or more brakes during the blanking interval, releasing one or more brakes of the vehicle, and automatically generating torque using one or more motors of the vehicle to propel the vehicle up the grade. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Reference will now be made briefly to the accompanying drawings, in which:

[0023] Figure 1 is a side view of a loading-transporting-unloading vehicle equipped with a system for preventing the vehicle from rolling backwards according to an embodiment of the present subject matter;

[0024] Figure 2 is a perspective view of another vehicle equipped with a system for preventing a vehicle from rolling backwards according to an embodiment of the present subject matter;

[0025] Figure 3 is a schematic diagram of a drive system and a system for preventing a vehicle from rolling backwards according to an embodiment of the subject matter of the present invention;

[0026] Figure 4 is a diagram showing a control procedure for preventing a vehicle from rolling backward according to an embodiment of the present subject matter;

[0027] Figure 5 is a diagram showing a control procedure for preventing a vehicle from rolling backward according to another embodiment of the present subject matter;

[0028] Figure 6 is a diagram showing a control procedure for preventing a vehicle from rolling backward according to another embodiment of the present subject matter;

[0029] Figure 7 is a diagram showing a control procedure for preventing a vehicle from rolling backward according to another embodiment of the present subject matter;

[0030] Figure 8 is a diagram showing a control procedure for preventing a vehicle from rolling backward according to yet another embodiment of the present subject matter;

[0031] Fig. 9 is a diagram showing a control procedure for preventing a vehicle from rolling backward according to an embodiment of the present subject matter;

[0032] Fig.10 is a graph illustrating the operation of a system for preventing a vehicle from rolling backwards according to an embodiment of the present subject matter;

[0033] Fig.11 is a schematic diagram of an electric drive and reduction system according to one embodiment;

[0034] Fig.12 is a block diagram showing a control system including a hydraulic friction brake and an electric retarder according to an embodiment;

[0035] Fig.13 A flow chart illustrating one embodiment of a method for controlling movement of a vehicle from a stopped position on a grade; and

[0036] Fig.14A flow chart illustrating an embodiment of a method for automatically controlling movement of a vehicle on a grade when no input is provided by an operator of the vehicle. DETAILED DESCRIPTION

[0037] Reference will be made in detail to exemplary embodiments of the subject matter of the present invention, examples of which are shown in the accompanying drawings. Whenever possible, the same reference numerals used throughout the drawings refer to the same or similar components. Although exemplary embodiments of the subject matter of the present invention are described with reference to a loading-hauling-unloading vehicle with a diesel engine used in the underground mining industry, embodiments of the subject matter of the present invention are also generally applicable to use with internal combustion engines and vehicles using such engines. For example, the vehicle can be an off-road vehicle designed to perform operations associated with a specific industry, such as mining, construction, agriculture, etc., and can include haul trucks, cranes, bulldozers, miners, agricultural equipment, tractors, material handling equipment, earthmoving equipment, etc. Alternatively or in addition, the vehicle can be a road vehicle, such as a tractor trailer, a road dump truck, etc. Moreover, other embodiments of the subject matter of the present invention are applicable to pure electric vehicles and mechanical equipment, such as battery-powered vehicles. As used herein, "electrical communication" or "electrical connection" refers to certain components configured to communicate with each other by direct or indirect signaling via direct or indirect electrical connection. As also used herein, "zero speed" refers to the state when the vehicle is stopped / stationary. A speed of "near zero" means very close to a stop (eg, in one embodiment, no more than 5 mph / 8 kph of travel, or in another embodiment, no more than 1 mph / 1.6 kph of travel).

[0038] Embodiments of the inventive subject matter relate to control systems (and related methods) for controlling a vehicle that prevent the vehicle from rolling backward on a slope. "Slope" refers to a non-horizontal surface having an inclination angle greater than or less than zero degrees. "Service brakes" refers to mechanical friction brakes, e.g., typically of the type where brake pads are actuated by an air / pneumatic or hydraulic system to engage a rotor or disc connected to a wheel or axle and are typically decoupled from the propulsion system.

[0039] Figure 1 A load-haul-dump vehicle 10 is shown to which the control system of the present subject matter may be incorporated. The LHD vehicle includes a front chassis 12 connected to a rear chassis 14 by an articulated joint 16. The vehicle 10 also includes a bucket 18 at the front thereof for pushing overburden and / or for moving overburden and / or mined material. The bucket 118 is operable by a hydraulic lift assembly (not shown). A cabin 20 is provided at the rear of the vehicle 10 in which a diesel engine (in the case of a diesel engine-driven vehicle) or a battery (in the case of an electric vehicle) for providing power to the vehicle 10 and its accessories are housed.

[0040] refer to Figure 2 , the vehicle may be a haul truck 30. Haul truck 30 is a dump truck specifically designed for high-volume mining and heavy construction environments. The drive system of the haul truck includes drive wheels 32, which are connected to a diesel-electric power / traction system that provides engine power to the haul truck. (Haul trucks and underground mining vehicles are general examples of vehicles, although in embodiments, the systems and / or methods of the subject invention are specifically implemented on a haul truck or an underground mining vehicle.)

[0041] Figure 3 An example of a drive system 100 for an electric drive machine such as an LHD vehicle 10 or a haul truck 30 is schematically shown. The drive system 100 includes a primary power source such as an engine 102 (e.g., a diesel engine, a gasoline engine, a multi-fuel engine, etc.) and a traction alternator / generator 104 mechanically connected to and driven by the engine 102. Figure 3 As shown in , the traction alternator 104 is electrically connected to a traction bus 106. The alternator 104 is configured to provide AC power to one or more rectifiers 108, which are electrically connected to one or more power converters, such as first and second inverters 110, 112, via the traction bus 106. The inverters 110, 112 are connected to one or more motors, such as a first traction motor 114 and a second traction motor 116 associated with a first wheel and a second wheel of the vehicle, such as the rear wheels of the vehicle 10 (including a first rear wheel 118 and a second rear wheel 120), respectively. Optionally, the vehicle may have a single motor or more than two motors. Although in Figure 3 10, but one or more embodiments of the subject matter described herein may be used with a single inverter and a single motor or with more than two inverters and more than two motors on a vehicle. The rectifier 108 is configured to convert AC power received from the alternator 104 to a DC output, which is then supplied to the inverters 110, 112 via the traction bus 106. The inverters 110, 112 are configured to provide three-phase variable frequency AC power to first traction motors 114 and second traction motors 116 associated with first wheels 118 and second wheels 120 of the vehicle 10 (typically the rear wheels of the vehicle).

[0042] As in Figure 310. As also shown in FIG. 10, in one embodiment, a starter motor 122 may be associated with the engine 102 for rotating the engine 102 to start operation, as is known in the art. In addition, the vehicle may include a battery 124, such as a 24V battery, which is electrically connected to the alternator 104 via a third winding 126 and an excitation winding 128. The battery 124 is configured to act as an alternator field static exciter to start operation of the electric drive system 100 of the vehicle 10.

[0043] The traction motors 114, 116 provide traction power to move the vehicle and may be either AC or DC electric motors. When a DC traction motor is used, the output of the alternator is typically rectified to provide appropriate DC power. When an AC traction motor is used, the alternator output is typically rectified to DC and thereafter inverted to three-phase AC before being provided to the traction motors 114, 116. During a propulsion mode of operation, power may be transferred from the engine 102 to the traction motors 114, 116, and thereby to the wheels 118, 120 of the vehicle 10 to achieve movement.

[0044] In addition to providing generating power, the traction motors 114, 116 may also provide braking or braking forces for controlling the speed of the vehicle 10 in which the drive system 100 is deployed. This is generally referred to as dynamic braking. During the dynamic braking mode of operation, for example, when the movement of the vehicle is blocked, electricity can be generated by the mechanical rotation of the drive wheels and directed to the deceleration grid 130. In particular, the kinetic energy of the vehicle 10 can be converted into rotational power at the drive wheels 118, 120. The rotation of the drive wheels can also rotate the motors 114, 116 to generate electricity, for example, in the form of AC power. The inverters 110, 112 can be used as a bridge to convert the power provided by the motors 114, 116 into DC power. The loss of the DC power generated by the motors 114, 116 can generate a reverse rotation torque at the drive wheels 118, 120 to decelerate the vehicle 10. Such losses can be completed by passing the generated current provided by the inverters 110, 112 through a resistor such as a dynamic braking grid 130 or a deceleration grid, as shown.

[0045] like Figure 3 As further shown in FIG. 1 , the drive system 100 also includes an engine radiator fan 132 driven by the engine 102 to provide cooling to the engine 102. The system 100 may also include one or more control and motor cooling fans 134 mechanically connected to the alternator 104. The cooling fans 134 are configured to provide cooling to all components of the traction drive system, such as the inverters 110, 112, the traction motors 114, 116, etc.

[0046] The alternator 104 may also be connected to a hydraulic pump 136 that provides hydraulic pressure for use by accessories or other components of the vehicle. For example, the hydraulic pump 136 may be configured to provide hydraulic pressure for use by the bucket arm 18 and / or brake devices, such as those associated with one or more wheels of the vehicle 10 (e.g., at Figure 3 One or more hydraulic service brakes 138, 140 are shown as being associated with wheels 118, 120. Figure 3 10 , alternatively, the vehicle may include a single brake or more than two brakes. The hydraulic service brakes 138 , 140 are operable to provide friction braking or braking effort to the wheels 118 , 120 of the vehicle 10 to stop or decelerate the vehicle, and may be used to supplement or replace the braking effort provided by the traction motors 114 , 116 when operating in a dynamic braking mode of operation. In one embodiment, the hydraulic service brakes 138 , 140 are fluidly connected to the hydraulic pump 136 and include one or more electro-hydraulic proportional valves 144 , the position of which may be controlled by a controller, as discussed below, to control the amount of braking effort provided by the brakes 138 , 140 . Other types of valves may also be utilized.

[0047] Although the vehicle 10 described herein is disclosed as including a braking device in the form of a hydraulic service brake, other types of service brakes may be utilized on the vehicle without departing from the broader aspects of the subject matter of the present invention. For example, the service brake may be any type of friction brake known in the art that utilizes a wear surface of a rotating or moving part that contacts (e.g., clamps or presses) a vehicle wheel to slow or stop the rotation of the wheel by friction to slow or stop the vehicle. The portion (e.g., a disc, a drum, etc.) that forces the wear surface of the friction brake against the wheel may be mechanically, hydraulically, pneumatically, or electromagnetically implemented. As used herein, "service brakes" may include vehicle parking brakes and / or wheel brake locks. Optionally, the brake applied may be one or more traction motors that are engaged to not rotate in a rearward direction (e.g., relative to a selected or previous direction of travel).

[0048] Regardless of the specific type of service brakes used, the brake devices 138, 140 may be manually deployed or activated by an operator of the vehicle, such as, for example, by stepping on a brake pedal in the cab or by pressing a button on a user interface, although other means of initiating frictional contact of the brakes with the rotating wheel components may also be utilized. In one embodiment, the application of the service brakes 138, 140 may also be automatically controlled by a controller or control unit of the vehicle. In particular, as in Figure 3As further shown in FIG. 1 , the drive system 100 and its various components, including the brake devices 138 and 140, may be electrically connected (or otherwise communicatively connected) to and controlled by a controller 142. The controller 142 may represent a hardware circuit that includes and / or is connected to one or more processors (e.g., one or more microprocessors, field programmable gate arrays, and / or integrated circuits). In particular, the controller 142 is configured to control the traction motor system 100 and its various components, and to control the power supplied to and from the traction motor system.

[0049] As discussed below, the controller 142 is also operable to automatically prevent the vehicle from rolling back when on a slope by coordinated control of the service brakes 138, 140 and the drive system 100. In particular, the control unit or controller 142 is configured to automatically apply the service brakes 138, 140 and / or control the torque output of the wheel motors 114, 116 to keep the vehicle 10 on a slope at zero speed or near zero speed during various operating conditions without input from the operator of the vehicle to prevent unintentional rolling back. As used herein, "automatically" refers to the absence of input or intervention from the operator of the vehicle. As used herein, a "rolling back condition" refers to a state or situation in which it is possible for the vehicle to move in a direction opposite to or different from the selected or desired direction of travel when there are no brakes or the accelerator pedal of the vehicle is not depressed.

[0050] For example, when the vehicle is traveling on a slope and the operator wishes to stop the vehicle, a backward slip state is possible. As the operator or control system releases the acceleration input device of the vehicle, such as the accelerator pedal (or otherwise manually or automatically stops the acceleration in the direction of travel), the vehicle will soon decelerate because the vehicle is traveling on a slope, and the vehicle will approach zero speed. In addition, due to the slope in the route, even if the operator continues to activate the acceleration input device (e.g., step on the pedal), the vehicle may decelerate. When the zero speed threshold is reached, the vehicle may slip backward in the absence of the application of the service brake or the parking brake. In order to prevent this backward movement, one or more brakes can be automatically activated and / or one or more motors can be automatically operated to generate torque in the opposite direction. This causes the vehicle to maintain its position on the route (e.g., not slipping backward) or the vehicle to move slightly backward at a controlled speed.

[0051] The movement of the vehicle in one or more directions may be determined using one or more sensors 300. These sensors 300 may include a global positioning system receiver, a reflective sensor, a discontinuous sensor, an optical encoder, a variable reluctance sensor, a Wiegand sensor, a Hall effect sensor, etc. The controller 142 may determine the direction of travel of the vehicle 10 based on the output of the sensors 300.

[0052] Figure 4A flow chart of one embodiment of a method 400 for preventing a vehicle from rolling backward is shown. The flow chart may represent operations performed under the direction of a control program executed by the controller 142 to prevent a vehicle from rolling backward when an operator desires to stop the vehicle on a grade. As shown therein, when the operator releases the accelerator pedal at 410, the controller 142 is configured to determine a target maximum deceleration based on load, vehicle speed, and / or estimated grade at 412, and is configured to control torque as needed at 414 to maintain vehicle deceleration to less than the maximum deceleration rate and slow the vehicle.

[0053] The weight of the load may be determined based on input provided to the controller 142 by an operator, a manifest, a sensor (e.g., a scale on which the load is positioned), or the like. The vehicle speed may be determined by one or more of the sensors 300, such as a global positioning system receiver, a tachometer, or the like. An estimated slope may be determined by input provided by an operator or by reference to a database including slopes at different locations along a route. Alternatively, one or more of the sensors 300 may include an inclinometer, accelerometer, or the like that may output data indicating the slope of the route or an estimated slope. The target maximum deceleration (or deceleration limit) may be decreased for heavier loads (or increased for lighter loads) in a direction opposite to the selected or previous direction of travel, decreased for slower vehicle speeds (or increased for faster vehicle speeds), and / or decreased for smaller slopes (e.g., flatter slopes) or increased for steeper slopes (e.g., more inclined slopes).

[0054] The drive system 100 is used to provide a controlled deceleration / slowing of the vehicle (rather than letting gravity control alone). For example, the torque generated by the motor of the drive system 100 can be controlled (e.g., automatically) to achieve a target deceleration of the vehicle and reduce the speed of the vehicle to a very low but non-zero speed. The vehicle and the motor of the vehicle can continue to operate in the selected direction of travel. That is, the vehicle may not start to slide downhill or stop moving to zero speed. As shown at 416, in one embodiment, the operator can then manually apply the service brakes 138, 140 at zero speed or at a very low speed close to zero (but positive). This allows the drive system 100 to prevent the vehicle from sliding back without applying any of the vehicle's brakes. For example, a torque applied by the motor of the vehicle that does not propel the vehicle in a selected direction of travel (e.g., uphill) but can also prevent the vehicle from sliding downhill can prevent the vehicle from sliding back downhill.

[0055] like Figure 4As further shown in , in one embodiment, the controller 142 may be configured to automatically apply the service brakes 138, 140 when the vehicle approaches zero speed under controlled deceleration but is still moving in the selected / desired direction of travel. In particular, the controller 142 determines whether there is a brake pedal input / deceleration command (e.g., input by an operator) or whether the accelerator pedal feedback exceeds a threshold at 418. If deceleration / braking is present (ON) or the accelerator pedal feedback exceeds the threshold and the vehicle speed is less than the threshold speed (i.e., when the vehicle approaches zero speed), the controller 142 applies the service brakes 138, 140 at 420, regardless of whether it is a controlled deceleration or an abnormal zero torque deceleration. However, if no accelerator pedal or brake feedback is received / detected and the vehicle speed is less than a threshold speed (i.e., when the vehicle is approaching zero speed), the controller 142 at 422 automatically applies the service brakes 138, 140 based on the brake delay time (i.e., the time it takes to engage the brakes and slow / stop the vehicle) and the vehicle deceleration at a speed threshold known to be at or near zero speed (but positive speed).

[0056] Further, at 424, if no accelerator pedal or brake input is received after a predetermined time has elapsed (e.g., by manual engagement of the brakes by an operator), then the brakes 138, 140 are released. In either embodiment, the brakes may be automatically applied based on the brake delay time (i.e., the time taken to engage the brakes and slow / stop the vehicle) and the vehicle deceleration at a speed threshold known to be at or near zero speed (but positive speed). For example, the controller 142 may be configured to apply the brakes earlier when decelerating at a faster rate and later when decelerating at a slower rate. Thus, the invention described herein provides a method for preventing a vehicle from rolling backward when stopping a vehicle on a grade, and provides a smooth transition from vehicle movement to a stop.

[0057] Another situation where a vehicle rolling backwards may occur is when starting the vehicle on a slope. When the vehicle is stopped on a slope, the drive system usually holds the brakes. Once the vehicle is stopped, the brakes are applied, or the brakes are automatically applied during deceleration, as described above. Figure 5A flow chart of one embodiment of a method 500 for preventing a vehicle from rolling backward when starting a movement on a slope is shown. The flow chart may represent operations performed or implemented by the controller 142 for preventing a vehicle from rolling backward when starting a vehicle on a slope. As shown at 510, first, the vehicle is stopped and the drive system (by the blocking action of the traction motor or by the application of the service brake (e.g., parking brake)) holds the vehicle in a stationary position. In one embodiment, at 512, the operator applies a braking / blocking force to maintain the vehicle position and depresses the accelerator pedal to increase the torque to start the movement. For example, the operator may select a travel direction (e.g., by providing input to the control system via one or more input devices) and apply the throttle to command the vehicle to move. When the torque available at the traction motor exceeds a threshold value (i.e., a balancing torque) sufficient to prevent rolling backward, the brake is released at 514 and the vehicle is allowed to move in the selected travel direction. Otherwise, the brake is continued to be held at 516 by the controller 142 until the torque exceeds the threshold. In one embodiment, the torque threshold may be selected based on the estimated slope.

[0058] As in Figure 5 As further shown in , some fault conditions may require other measures to be taken. For example, the drive system torque control and the drive system brake control may not be usable or available. If such a fault condition exists, the controller 142 is configured to release the brakes 138, 140 at 518 to prompt the operator to act. At 520, if the fault condition is removed, the controller 142 controls the drive system 100 as usual to respond to the operator / pedal input. In another embodiment, the drive system brake control may be available and functional, but the drive system torque control may not be. In this case, at 522, the controller 142 is configured to keep the brakes 138, 140 during such a fault condition. If the fault is removed, the control program proceeds to the initial state 510. However, if the fault is not removed after a predetermined time, the controller 142 releases the brakes 138, 140 at 524 when the fault still exists to prompt the operator to take action (e.g., apply the service brake, press the override switch, control movement, etc.).

[0059] Still further reference Figure 5In one embodiment, at 526, the operator may not apply any braking or acceleration input / throttle command or the operator may release the brakes (or remove the commanded deceleration force). In this case, at 528, the controller 142 waits for a pedal input (e.g., deceleration / brake / throttle feedback) for a predetermined time. If a pedal input is received within the predetermined time / window, the control process proceeds to step 512. However, if no pedal input is received within the window, at 530, the controller 142 controls the drive system 100 to release the brakes 138, 140, and / or remove any deceleration force. In this case, under the control of the controller 142, the drive system 100 applies torque at 532 to allow very low positive or negative speeds, or to allow acceleration to a predetermined speed limit. That is, the drive system 100 is used to allow very low speeds in the direction of gravity (i.e., limit the rolling speed and prompt the operator to take some action). At 534 , the very low positive or negative speed continues until the operator commands an acceleration torque or the operator stops the vehicle using the brake / decel pedal.

[0060] Now go to Figure 6 , a flow chart of one embodiment of a method 600 for controlling a vehicle during a rolling back condition is shown. The flow chart may represent operations performed or implemented by the controller 142 during a rolling back condition. A rolling back condition may occur, for example, due to a drive system failure (e.g., a failure to propel), if an operator changes the selected direction of travel, or if the vehicle decelerates too quickly, passes zero speed and begins to roll in the opposite direction before the brakes can be applied. Figure 6 In one embodiment, if the speed of the vehicle exceeds a threshold speed stored in memory (i.e., a negative speed indicating a backward roll) and vehicle movement is detected in a direction opposite to the selected direction of travel, the controller 142 is configured to automatically control the traction motors 114, 116 to provide a deceleration force to slow the vehicle, as shown at 612. Figure 3 One or more sensors 300 shown in can determine vehicle movement in one or more directions. In one embodiment, the threshold speed can be about 6 mph. In one embodiment, the controller 142 is configured to control the drive system 100 to maintain the vehicle speed at about 3 mph.

[0061] As in Figure 6100, if the vehicle speed exceeds a threshold speed stored in the memory (i.e., a negative speed indicating slippage) and the selector is in a neutral state, the controller 142 is configured to automatically control the traction motors 114, 116 to provide a deceleration force to slow the vehicle, as shown at 614. In one embodiment, the threshold speed may be approximately 5 mph. In one embodiment, the controller 142 is configured to control the drive system 100 to maintain the vehicle speed at approximately 3 mph.

[0062] In one embodiment, if the speed of the vehicle does not exceed the threshold speed but is still experiencing a rollback condition, at 616, the controller 142 may automatically apply the brakes 138, 140. This may occur, for example, if the vehicle is stopped in a negative speed state. Alternatively, at 616, the brakes may be automatically applied or otherwise activated in response to the speed of the vehicle not exceeding the threshold speed (also referred to as the upper speed limit) without the rollback condition occurring or being detected. For example, if the vehicle is nearly balanced on the slope and has a very low acceleration (e.g., approaching zero speed) in the expected or selected direction of travel, the brakes may be applied at a very low speed that does not exceed the upper speed limit (e.g., 30 motor revolutions per minute), regardless of whether the acceleration is or is close to zero. This may result in the application of the brakes without the vehicle rolling backward down the slope or without detecting the vehicle rolling backward down the slope (e.g., a rollback condition). As shown at 618, the controller 142 may then automatically release the brakes and control the traction motors 114, 116 to provide torque to allow slow creep after a fixed time. In one embodiment, if the brakes are set during the rollback condition, the operator may be required to apply and release the brakes before the vehicle moves.

[0063] Figure 7A flow chart of one embodiment of a method 700 for controlling vehicle movement is shown. The flow chart may represent operations performed or implemented by the drive system 100 or the controller 142. In one embodiment, the drive system 100 may be controlled by an initial state in which the vehicle is stopped on a slope and the drive system is holding the brakes. The method 700 begins with a motion command 710 in which the operator commands movement by applying at least 50% of the throttle. In response to the motion command 710, the drive system 100 increases the torque to the command torque or increases to a maximum torque (rather than a balanced torque that only holds the vehicle stationary on the slope). For example, the controller 142 may determine a torque threshold (e.g., based on the throttle setting selected by the operator), that is, the amount of torque required to achieve the desired acceleration. The torque threshold may be based on the weight of the vehicle, the weight of the load carried by the vehicle, the slope on which the vehicle is stopped, etc. The drive system 100 may then increase the torque generated by the motor of the vehicle to the torque indicated by the operator or to the maximum torque that the motor can generate. In one embodiment, as shown at 712, the controller 142 can control the system 100 to provide the maximum amount of available torque and automatically release the brakes at the maximum torque (rather than the threshold torque for the desired speed). In another embodiment, the controller 142 can hold the brakes for a predetermined (e.g., non-zero) time after the accelerator pedal is applied, and then release the brakes. In this embodiment, the controller 142 uses a time delay before releasing the brakes. In another embodiment, the controller 142 can prompt the operator to release the brakes, as shown at 716. In particular, the controller 142 can indicate to the operator, for example, through an audio alarm or a visual display, that the threshold torque is available and the system is ready to release the brakes. In yet another embodiment, the operator can take over control of the braking function. For example, at 718, the controller 142 can require the operator to apply the service brakes 138, 140, and then automatically release the brakes after the accelerator pedal is depressed. Then, a balancing torque can be applied to maintain zero or slightly positive speed, and the torque can be increased as required by the accelerator pedal.

[0064] Fig.13A flow chart of an embodiment of a method 1300 for controlling movement of a vehicle from a stopped position on a slope is shown. Operations described in conjunction with the method 1300 may be performed or implemented by the controller 142 and / or the drive system 100. The method 1300 may provide a closed-loop process for controlling vehicle acceleration after the brakes are released when the vehicle is on a slope. At 1302, one or more brakes of the vehicle are engaged to hold the vehicle in place on the slope. The brakes may be used according to one or more embodiments of the subject matter of the invention described herein or may be engaged according to another process. At 1304, it is determined whether the brakes are released. For example, the controller 142 may release the brakes in response to receiving an operator input. If the brakes are released, the process of the method 1300 may proceed to 1306. Otherwise, the process of the method 1300 may return to 1302.

[0065] At 1306, after releasing the brakes and in response to releasing the brakes, the vehicle is allowed to roll back slightly and / or accelerate rapidly down the slope. For example, the controller 142 may allow the drive system 100 to disengage the brakes without generating motor torque or by generating some motor torque to allow the vehicle to roll back down the slope for a small amount, such as a specified threshold distance of less than one meter (or another distance) along the length of the route, before directing the motor to generate torque to propel the vehicle up the slope. As another example, the controller 142 may direct the drive system 100 to accelerate rapidly using the motor. The controller 142 may direct the drive system 100 to accelerate faster to an operator-selected or automatically implemented throttle position than the drive system 100 would otherwise accelerate (e.g., when not starting to move up the slope from a stopped position). At 1308, the torque generated by the motor of the drive system 100 is rapidly adjusted to smoothly transition from a stopped vehicle position to movement according to an operator-selected or automatically implemented throttle position. For example, sharp accelerations implemented by the drive system 100 may be reduced while still moving the vehicle up a grade from a stopped position without vehicle jolts or other sudden movements.

[0066] Fig.14A flow chart of an embodiment of a method 1400 for automatically controlling movement of a vehicle on a slope when an operator of the vehicle does not provide input is shown. The operations described in conjunction with the method 1400 may be performed or implemented by the controller 142 and / or the drive system 100. At 1402, one or more brakes of the vehicle are engaged to hold the vehicle in place on the slope. The brakes may be engaged according to one or more embodiments of the subject matter of the invention described herein or according to another process. At 1404, it is determined whether the operator of the vehicle has provided input within a specified blanking interval. For example, the controller 142 may determine whether the operator has stepped on a brake pedal, a start button, or other actions to provide input to the controller 142 to keep the brakes engaged. The controller 142 may periodically check the operator input to determine whether the operator has provided input to keep the brakes engaged, for example, at least once every five seconds (or other time interval) per blanking interval. If the operator has provided input to keep the brakes engaged, the flow of the method 1400 may return to 1402. Otherwise, if the operator does not provide input during the blanking interval, flow of method 1400 may proceed to 1406 .

[0067] At 1406, the brakes of the vehicle are released. At 1408, motor torque is generated to move the vehicle up the grade in a slow creeping manner. For example, simultaneously with (or shortly thereafter) the brakes of the vehicle are disengaged, the controller 142 may direct the motor of the drive system 100 to begin generating a small amount of torque to move the vehicle up the grade at a slow speed (e.g., less than five kilometers per hour).

[0068] In certain embodiments, both operator and automatic control can be used to transition from stop to move in a selected direction of travel without unexpected rollback, such as by Figure 8 As shown in the flowchart of method 800 shown in FIG. Figure 4 As discussed, after the operator releases the accelerator pedal, the controller 142 may determine a target maximum deceleration and control the drive system to provide torque as needed to limit the maximum deceleration rate. This allows the vehicle to be decelerated to a very low speed and maintain the commanded direction of travel, as shown at 810. The operator may then apply the service brakes or parking brakes at zero speed to maintain the vehicle in a stationary state, as shown at 812. Depending on the stationary state, various control strategies are contemplated that allow a certain level of operator input when transitioning from a stationary state to moving in the selected direction of travel.

[0069] The first control strategy 820 includes the operator setting the wheel locks and releasing the previously applied service or parking brakes at 822 to keep the vehicle stationary on the grade. As shown at 824, both manual and automatic control are then used to smoothly transition the vehicle from a stop to a selected direction of travel when accelerator feedback is detected. In particular, the controller 142 is configured to first command the service or parking brake to be turned on when the wheel locks are in the open state (from step 822) and the accelerator pedal feedback exceeds a threshold. The operator may then be prompted to unlock the wheel locks. Once the wheel locks are closed, the controller 142 is configured to automatically release the service or parking brakes when the available torque threshold is met, as discussed in the above-mentioned embodiments (i.e., when sufficient torque is available to prevent backward slip).

[0070] The second control strategy 830 includes the controller 142 automatically applying the service brakes at 832 after the operator applies the brakes to bring the vehicle to zero speed. As discussed in the above embodiments, the controller 142 is configured to automatically release the brakes at 834 when the operator applies the accelerator pedal and the available torque exceeds a threshold level sufficient to prevent the vehicle from rolling backward. This control allows the vehicle to transition from a stationary state to smooth movement in the selected direction of travel.

[0071] Likewise, the third control strategy 840 includes the controller 142 automatically applying the service brakes at 842 after the operator applies the brakes to bring the vehicle to zero speed. The operator may then hold the brakes and apply the accelerator pedal to begin moving the vehicle on the grade. In conjunction with this, the controller 142 is configured to automatically release the brakes when the available torque exceeds a threshold level sufficient to prevent the vehicle from rolling backward, as shown at 834. In one embodiment, the brake pressure may be slowly reduced as the balancing torque is applied.

[0072] In one embodiment, when starting the vehicle on a slope, the operator (in manual start mode) or the controller 142 (in automatic start mode) can use a hydraulic brake that can be applied variably or a hydraulic brake with a flow limiting valve to balance both brake and torque application to prevent backward slip. As the torque increases, the brake can be slowly relaxed, for example by reducing the brake pressure. In this way, the brake operates similar to a clutch, thereby balancing the torque and brake application to prevent the vehicle from slipping and smoothly transitioning to positive motion. In one embodiment, the brake can be a hydraulic brake with an associated flow limiting valve, which can be controlled by the controller 142 so that the brake pressure can be selectively reduced as the torque increases. The torque increase rate (ramp rate) can be adjusted to match the known brake pressure and the torque rate of the brake to maintain zero speed. The system can be configured to continue to adjust the applied torque increase rate and brake pressure drop until the brake is fully released. In both cases (i.e., a variably applied hydraulic brake or a hydraulic brake with a flow limiting valve), after the brake is fully released, the continued application of torque enables the movement of the vehicle. If excessive vehicle movement is detected that indicates a fault condition (eg, accelerating too quickly), the brakes may be automatically applied to stop the vehicle's motion.

[0073] In addition to ensuring that the vehicle is prevented from rolling back when stopped on a slope and when starting on a slope, the system and method of the subject of the present invention also allow for an increased level of control of the transition from forward motion to reverse motion, and vice versa. For example, when the drive system inverter is turned off, the operator can request a change of direction at the speed by changing the selector to the opposite direction (e.g., forward to reverse, or reverse to forward) instead of commanding a neutral gear. In this case, the controller 142 is configured to determine whether to enter deceleration based on gravity estimation and vehicle acceleration. In one embodiment, if driving down along a large slope, the controller 142 controls the drive system 100 to provide a controlled deceleration to zero speed. In particular, the controller 142 is configured to refuse to give a driving torque in the required direction if the vehicle speed exceeds a threshold and travels in the direction opposite to the required direction. Once the vehicle speed is reduced to below the threshold using controlled deceleration, the controller 142 is then configured to apply the brake based on the received torque command, the torque threshold on the slope, and the vehicle speed, so that the brake is maintained until the available torque in the newly selected driving direction is sufficient to prevent the vehicle from rolling back.

[0074] However, if the vehicle is traveling on a relatively flat surface, the controller 142 controls the drive system to switch to a deceleration mode based on the vehicle speed and acceleration and interprets the accelerator pedal feedback as a deceleration command. The drive system 100 automatically stops the vehicle using the service brakes based on the received torque command, the torque threshold on the slope, and the vehicle speed, so that the brakes are maintained until the available torque in the newly selected direction of travel is sufficient to prevent the vehicle from rolling back. If the propulsion command is insufficient to prevent rolling back, the brakes are applied and maintained to prevent rolling back. If the propulsion command is sufficient to prevent rolling back, the vehicle is allowed to transition to driving in the manner described above.

[0075] Optionally, the drive system 100 and accompanying methods described herein can prevent a vehicle from rolling backward on a slope by applying direct current to an AC motor of the vehicle. The controller 142 can determine the specified amount of direct current from a previously determined amount or based on the load, slope, and / or speed of the vehicle (moving up the slope). For heavier loads, steeper slopes, and / or faster speeds, the controller 142 can calculate a larger amount of direct current. For lighter loads, flatter slopes, and / or slower speeds, the controller 142 can calculate a smaller amount of direct current.

[0076] Then, a determined amount of direct current is applied or provided to one or more AC motors 114, 116 of the drive system 100. In one embodiment, the amount of direct current applied to the motors 114, 116 is the maximum amount of direct current that the drive system 100 can provide to the motors 114, 116. Alternatively, the amount of direct current applied to the motors 114, 116 is less than the maximum amount of direct current that the drive system 100 can provide to the motors 114, 116. The current is applied to the motors 114, 116 without engaging or otherwise activating the brakes of the vehicle. The direct current provided to the motors 114, 116 prevents the motors 114, 116 from moving in the opposite direction (e.g., to cause or allow the vehicle to slide backward down a slope). In this way, the direct current causes the motors 114, 116 to operate as brakes without applying any brakes of the vehicle. Optionally, one or more brakes of the vehicle may also be applied to maintain the position of the vehicle.

[0077] The applied brakes (or any brakes previously applied) may be released as direct current continues to be provided to the motors 114, 116. For example, the controller 142 may activate or otherwise control a switch that can control the flow of direct current to the motors 114, 116. By disengaging the brakes of the vehicle while maintaining the direct current applied to the motors 114, 116, the vehicle may be prevented from rolling backward down the grade as the motors 114, 116 transition to anti-skid control and generate a holding torque that can counteract the force of gravity pulling the vehicle down the grade.

[0078] Alternatively, the controller 142 may apply maximum or 100% AC to the motors 114, 116 just before the vehicle is about to stop on the grade or roll back, and then apply one or more brakes of the vehicle before the vehicle comes to a complete stop. For example, as the vehicle moves up the grade, the controller 142 may increase the AC provided to the motors 114, 116 to the maximum amount that the drive system 100 can provide to the motors 114, 116 (without damaging the motors 114, 116), and then apply the vehicle's brakes when the vehicle comes to a complete stop (e.g., when the vehicle's speed is zero).

[0079] In another embodiment, the controller 142 can operate as a speed regulator when the vehicle is traveling up a slope and is about to stop. The controller 142 can control the torque generated by the motors 114, 116 when the vehicle is decelerating and is traveling at a low speed (e.g., no more than six kilometers per hour or another speed). The controller 142 can provide current to the motors 114, 116 at the fundamental excitation frequency of the motors 114, 116 to control the motors 114, 116 and stop the vehicle on the slope without the vehicle rolling back down the slope.

[0080] In another embodiment, the present subject matter provides a system and method for reducing the speed of a vehicle using a deceleration force provided by a traction motor of the vehicle. For example, first, the vehicle may be moving in the desired direction of travel, and the operator may request full / maximum deceleration force to stop the vehicle. If the deceleration request is by a lever or other means that does not require the operator to actively hold the lever to achieve deceleration of the vehicle, the traction motor decelerates the vehicle to a low, near zero speed and maintains the low speed. If the deceleration request is by a rebound pedal or similar mechanism, the traction motor decelerates the vehicle to a low, near zero speed and then stops the vehicle using the service brakes. In one embodiment, the operator may then use the service brakes or parking brakes to keep the vehicle stopped. In one embodiment, in the case of use, the operator may keep the vehicle stopped by continuously depressing the deceleration pedal. In this case, if the operator then releases the deceleration pedal, the controller 142 is configured to command the traction motor to maintain the stopped state (zero speed) for a predetermined amount of time. If the vehicle is equipped with an override switch, the accelerator pedal, when depressed, allows the rollback speed to be controlled by deceleration after a time delay. If the vehicle does not have an override switch, the vehicle is allowed to accelerate to the opposite motion threshold. If the operator applies the accelerator pedal, the zero speed condition will continue to be maintained until a sufficient amount of torque is available to prevent rolling back and move the vehicle in the intended direction of travel, as described above.

[0081] In conjunction with the above, in one embodiment, the vehicle may include an override switch configured to send an override signal to the controller 142 to enable the operator to disable the above-mentioned set control program. For example, at various different times during the operation of the vehicle, the operator may wish to take over all control of the vehicle, rather than having the controller 142 instruct the vehicle to accelerate, decelerate, stop and move. In particular, the operator may want to be able to coast in the direction opposite to the selected direction of travel, such as when turning on a gentle slope. In this case, the operator can press the override button or otherwise enable the override to disable the above-mentioned automatic application of brakes and allow coasting backwards (coast-back). In one embodiment, the controller 142 can still be configured to automatically apply the brakes or use the traction motor to decelerate or stop the vehicle if the backward coasting caused by the override causes an overspeed or overacceleration situation (i.e., the speed or acceleration exceeds a safety threshold).

[0082] In one embodiment, the system of the subject of the present invention also includes a redundant braking or notification function that is automatically implemented in the event of a drive system failure or failure. For example, when the vehicle is on a slope, if the drive system card suddenly fails or loses power, if the system does not apply the brakes, then backward slip will occur. In this scenario, the operator may not pay attention and may think that the brake will be automatically applied according to the above-mentioned automatic control to prevent backward slip. Therefore, the system can be equipped with a redundant braking function, which will be automatically implemented before or after the backward slip state when the drive system failure is detected and the vehicle speed exceeds the threshold. In one embodiment, the brake can be applied to control the deceleration to zero speed. In one embodiment, the system can also be configured to output an audible or visual warning to the operator so that the operator knows that the anti-backward slip control described in the text will not work. This provides the operator with an alarm that the drive system will not be able to apply the brake and manual operation is necessary to prevent the backward slip state. This protective measure ensures that the operator can pay attention to and alert the operator that the automatic anti-backward slip function is unavailable.

[0083] In one embodiment, the control system of the subject invention, by utilizing the above-mentioned functions, is configured to provide controlled deceleration of the vehicle and automatic engagement of the service brakes while the vehicle is still moving in the expected direction of travel to prevent the vehicle from rolling back when stopped. That is, the service brakes are applied based on the acceleration / deceleration of the vehicle before crossing zero speed. The system of the subject invention is further configured to prevent rolling back when starting the vehicle from stopping on a slope by determining a torque threshold to achieve an expected acceleration (rather than speed) or by performing a maximum or preset target torque start instead of a threshold torque start. Due to the control strategy proposed in the text, a vehicle using the control system of the subject invention is more user-friendly and requires less skills to operate. In addition, the control system of the subject invention can update existing vehicles by modifying the control software without a large number of hardware upgrades or modifications.

[0084] In one embodiment, a method for controlling a vehicle is provided. The method includes the steps of controlling at least one traction motor of the vehicle to provide a controlled deceleration of the vehicle when traveling on a grade in a selected direction of travel, and automatically applying the service brakes of the vehicle as the vehicle moves in the selected direction of travel.

[0085] In another embodiment, a system is provided. The system includes: a control unit configured to be electrically connected to a drive system of a vehicle, the drive system including at least one traction motor for providing a traction force to the vehicle and a service brake associated with at least one wheel of the vehicle. In the absence of a command to provide a traction force in a selected direction of travel, the control unit is configured to automatically apply the service brake when the vehicle moves in the selected direction of travel to prevent the vehicle from rolling backward.

[0086] In one embodiment, the controller 142 is also operable to prevent the vehicle from rolling back through automatic application of the service brakes 138, 140 when on a grade or when pushing a pile of topsoil. When using an existing LHD vehicle 10 to push a pile of topsoil, for example, after the operator releases the accelerator pedal and before he / she can manually engage the service brakes, the spring tension in the dipper arm 18 and the slope at which the vehicle is in the pile of topsoil may cause the vehicle to inadvertently roll back several feet. However, in accordance with an embodiment of the inventive subject matter described herein, the control unit or controller 142 is configured to automatically apply the service brakes 138, 140 when a roll back condition is detected to maintain the vehicle 10 at or near zero speed on a grade and / or when pushing a pile of topsoil / burden, without input from the operator of the vehicle, so as to prevent such inadvertent roll back. As used herein, "automatically" means without input or intervention from the operator of the vehicle. As used herein, a "rollback condition" refers to a situation or condition in which vehicle movement in a direction opposite or different from a selected or desired direction of travel is possible in the absence of braking or the accelerator pedal of the vehicle being depressed.

[0087] For example, in one embodiment, the controller 142 is configured to continuously or intermittently monitor or detect the selected direction of travel (i.e., forward or reverse) of the vehicle and the speed of the motors (e.g., one or more of the traction motors), and is configured to immediately command engagement of the service brakes 138, 140 associated with the wheels 118, 120 of the vehicle 10 when a rollback condition is detected. In one embodiment, a "rollback condition" exists when the motor speed in a direction opposite to or different from the selected direction of travel exceeds a predetermined threshold. As used herein, "opposite to or different from the selected direction of travel" means, for example, that the motor rotates in a direction opposite to that required to achieve movement of the vehicle in the selected direction of travel or in a mode different from that required to propel the vehicle along the selected direction of travel (e.g., a regenerative braking mode).

[0088] In one embodiment, the threshold motor speed may be between about 0 rpm and about 100 rpm in a direction opposite or different from the direction of travel that prompts automatic application of the service brakes to prevent rolling back. In another embodiment, the threshold speed may be between about 10 rpm and about 90 rpm. In another embodiment, the threshold motor speed may be between about 20 rpm and about 80 rpm. In another embodiment, the threshold motor speed may be between about 30 rpm and about 70 rpm. In another embodiment, the threshold motor speed may be between about 40 rpm and about 60 rpm. In yet another embodiment, the threshold motor speed may be about 50 rpm in a direction opposite to the selected direction of vehicle travel.

[0089] In one embodiment, the vehicle 10 has a fixed gear ratio of approximately 90:1, so that the 50 rpm threshold for engagement of the service brakes (in the direction opposite to the selected direction of travel) is not perceptible to an observer or operator as movement. In one embodiment, the controller 142 is configured to apply the service brakes 138, 140 to prevent rollback within approximately 100 milliseconds of detecting a vehicle rollback condition. In one embodiment, the brakes 138, 140 may be maintained in a fully open or engaged state by the controller 142 until the selected direction of travel is changed by the operator to match the direction of the motor and / or by the operator depressing or activating the accelerator pedal.

[0090] Reference now Fig. 9 , a method 200 for controlling a vehicle to prevent the vehicle from rolling backward according to an embodiment of the present invention is shown. As shown therein, at 202, a selected direction of travel of the vehicle is detected and recorded by the controller 142. The speed and direction of at least one traction motor (e.g., the motors 114, 116 of the vehicle 10) are also monitored. At 204, the controller 142 determines whether the direction of the motor is opposite to the selected direction of travel. If not, no automatic measures related to the application of the service brake are taken. If the motor direction is opposite to the selected direction of travel, at 206, the controller 142 then (or simultaneously) determines whether the motor speed exceeds a threshold speed. If not, no automatic measures related to the application of the service brake are taken. However, if the speed detected by the motor in the direction opposite to the selected direction of travel exceeds the threshold speed, at step 208, the controller 142 automatically engages the service brake to prevent the vehicle from rolling backward. As described above, the service brake remains engaged until the operator of the vehicle changes the selected direction of travel to match the motor direction and / or the operator depresses the accelerator pedal.

[0091] Fig.10A graph 1000 illustrating the operation of a vehicle rollback prevention system is shown, with line 1002 representing motor speed, line 1004 representing brake percentage on, line 1006 representing a "reverse" selected direction of travel, line 1008 representing a "forward" selected direction of travel, and line 1010 representing the accelerator pedal being depressed. At 1012, the forward motor speed exceeds a threshold motor speed of 50 rpm while the vehicle is traveling in the reverse selected direction of travel. At 1014, the service brakes are then automatically activated to 100% engagement / open by the controller to prevent the vehicle from rolling back. At 1016, the operator (or the controller automatically) switches the vehicle from reverse to forward, and at 1018, the accelerator pedal is depressed to move the vehicle forward. At 1020, the controller then disengages the service brakes.

[0092] In one embodiment, the control system or controller of the present invention, by utilizing the above-mentioned functionality, is configured to automatically engage the service brakes whenever a rollback condition is sensed. This prevents the vehicle from rolling backward on a slope or when pushing a pile of topsoil, etc., without the need for operator input or action, and ensures that when the vehicle is in a forward or reverse direction, movement of the vehicle in a direction other than the selected direction is impossible. By managing vehicle movement in this manner, the control system of the subject invention ensures that rollback or vehicle movement in a direction other than the selected direction can be prevented. Therefore, vehicles using the control system of the subject invention are more user-friendly and require less skill to operate. In addition, the control system of the subject invention can be retrofitted (or added) to existing vehicles by modifying the control software (e.g., to direct the controller to operate as described herein) without extensive hardware upgrades or modifications.

[0093] In one embodiment, a method for controlling a vehicle is provided. The method includes the steps of determining a selected direction of travel of the vehicle, monitoring the direction of operation of a motor of the vehicle, monitoring the speed of the motor, and automatically applying the service brakes of the vehicle when a backward slip state is detected to prevent the vehicle from sliding backward. In one embodiment, the backward slip state exists when the direction of operation of the motor is different from the selected direction of travel. In one embodiment, the backward slip state exists when the speed of the motor exceeds a threshold speed. In one embodiment, the vehicle is a loading-transporting-unloading vehicle. In one embodiment, the service brakes are hydraulic or pneumatic service brakes. In one embodiment, the method may also include the step of disengaging the service brakes when the selected direction of travel matches the direction of operation of the motor and the accelerator pedal of the vehicle is depressed. In one embodiment, the threshold speed is between about 0 rpm and about 100 rpm. In other embodiments, the threshold speed is between about 40 rpm and about 60 rpm. In other embodiments, the threshold speed is about 50 rpm. In one embodiment, the vehicle has a fixed transmission ratio of about 90:1.

[0094] In another embodiment, a system is provided. The system includes: a control unit configured to be electrically connected to a drive system of a vehicle, the drive system including at least one traction motor for providing a driving force to the vehicle; and a service brake associated with at least one wheel of the vehicle. The control unit is configured to automatically apply the service brake when a backward rolling condition is detected to prevent the vehicle from backward rolling. In one embodiment, the control unit is configured to monitor the running direction of at least one traction motor and the speed of at least one traction motor. In one embodiment, the backward rolling condition exists when the running direction of at least one traction motor is different from the running direction of the motor corresponding to the selected driving direction of the vehicle and the speed of the at least one traction motor exceeds a threshold speed. In one embodiment, the control unit is configured to disengage the service brake when the selected driving direction matches the running direction of at least one traction motor and the accelerator pedal of the vehicle is depressed. In one embodiment, the service brake is a pneumatic or hydraulic brake. In one embodiment, the threshold speed is about 50 rpm. In one embodiment, the vehicle has a fixed gear ratio of about 90:1.

[0095] In other embodiments, a vehicle is provided. The vehicle includes a drive system including a traction motor drivingly connected to the wheels of the vehicle, the motor being configured to provide a motive force to propel the vehicle in a selected direction of travel in a propulsion mode of operation; a controller electrically connected to the drive system; and a friction brake associated with at least one wheel of the vehicle. The controller is configured to automatically engage the friction brake when a backward slip condition is detected to prevent the vehicle from backward slipping. In one embodiment, the controller is configured to monitor the direction of operation of the motor and the speed of the motor. In one embodiment, a backward slip condition exists when the direction of operation of the motor is different from the selected direction of vehicle travel and the speed of at least one traction motor exceeds a threshold speed. In one embodiment, the threshold speed is approximately 50 rpm and the vehicle has a fixed gear ratio of approximately 90:1. In one embodiment, the vehicle is a loading-hauling-unloading vehicle.

[0096] Additional embodiments of the inventive subject matter relate to control systems and methods (e.g., brake control) for controlling the transition from friction brakes to electric power (and vice versa) within a vehicle to automate the operation of starting and stopping the vehicle while on an inclined (greater than zero) grade. According to one aspect, for example, the control system (and associated method) is configured to simultaneously control the vehicle's electric drive system and friction brake system to prevent rolling back when operating the vehicle to move from a stopped position on an inclined grade. According to another aspect, the control system (and associated method) is configured to simultaneously control the vehicle's electric drive system and friction brake system to stop the vehicle and keep the vehicle stopped while traveling on an inclined grade.

[0097] exist Fig.11Another embodiment of an electric drive system 100 is shown in FIG. The electric drive system 100 is at least partially housed within the vehicle 10, 30 and includes a three-phase alternating current (AC) generator / alternator 1108 connected to be mechanically driven by an engine 1106 (e.g., a diesel engine). The AC output of the generator 1108 is supplied to one or more rectifiers 1110 configured to convert the AC output of the generator / alternator 1108 to a direct current (DC) output. The DC output of the rectifier 1110 is supplied to a DC bus, which (among other loads) is supplied to a set of inverters 1112, 1114. The inverters 1112, 1114 are configured to convert DC power from the DC bus into controlled three-phase variable frequency AC power. The outputs of the inverters 1112, 1114 are electrically connected to the electric motors 1102, 1104 (respectively), and the AC power output by the inverters 1112, 1114 has a waveform suitable for driving the electric motors 1102, 1104. The electric motors 1102, 1104 are operably connected to the drive wheels of the first set of wheels of the vehicle (e.g., the rear wheels). For example, the motors 1102, 1104 may be three-phase AC induction wheel motors. If the second set of wheels of the vehicle are drive wheels, the electric drive system 100 may include additional inverters and motors that are similarly Fig.11 The inverters 1112, 1114 and motors 1102, 1104 are connected in this manner.

[0098] As in Fig.11 As further shown in FIG. 1 , a drive system control unit or controller 1116 is electrically connected to the electric drive system 100. For example, the drive system control unit may be connected to the inverters 1112 and 1114. Among other tasks, the drive system control unit 1116 is configured to determine a desired torque request signal and send the desired torque request signal to the inverters 1112 and 1114. The torque request signal is processed by the control unit for the inverters 1112 and 1114 to drive the motors 1102 and 1104 to the desired torque output magnitude and in the desired rotational direction corresponding to the expected direction of movement of the vehicle. The control unit is also configured to control the motors 1102 and 1104 to provide a deceleration traction force to the wheels (e.g., the rear wheels) to decelerate or stop the vehicle. In particular, when operating in an electric braking mode, also known as electric deceleration, the electric motors 1102 and 1104 are reversed to charge the generator, and the drive wheels of the vehicle drive the electric motors 1102 and 1104. The drive motors 1102, 1104 apply torque to the drive wheels and cause them to slow, thereby braking the vehicle. In one embodiment, the control unit 1116 includes one or more microprocessors operating according to a set of stored instructions to provide vehicle control, as discussed in detail below and elsewhere herein.

[0099] Fig.12One embodiment of a control system (e.g., a brake control system) or control unit 1116 is shown in more detail. The control system 1116 includes a friction brake system 1222, which includes a first (e.g., rear) friction brake unit 1220 (e.g., a friction brake activation unit) associated with a first set of wheels 1212 (e.g., rear wheels) of the vehicle and a second (e.g., front) friction brake unit 1218 (e.g., a friction brake activation unit) associated with a second set of wheels 1214 (e.g., front wheels) of the vehicle. In one embodiment, the friction brake system 1216 is a hydraulic brake system, which further includes a first (e.g., rear) brake solenoid valve 1226 and a second (e.g., front) brake solenoid valve 1224, the first brake solenoid valve 1226 is controllable to control the pressure of hydraulic oil added to the first friction brake unit 1220, and the second brake solenoid valve 1224 is controllable to control the pressure of hydraulic oil added to the second friction brake unit. In other embodiments, other means for activating the first and second friction brake units 1218, 1220 may also be utilized without departing from the broader aspects of the present subject matter. In either (or either) embodiment, each friction brake unit may include, for example, various components for controllably applying friction loads to moving parts associated with wheels 1212, 1214, such as brake pads operably connected to axles or brake discs / rotors, hydraulically actuated calipers for applying force to brake pads against discs / rotors, etc. The control system 1116 further includes a friction brake control unit 1227, which is configured to control the application of the first and second (e.g., rear and front) friction brake units 1220, 1218 at least partially in response to operator input such as depressing a brake pedal.

[0100] In one embodiment, the drive system control unit 1116 and the friction brake control unit 1227 are electrically connected to each other and may be generally referred to as one or more controllers 1229. Fig.12 While drive system control unit 1116 and friction brake control unit 1227 are shown as separate components, control units 1116, 1227 may be integrated into a single control unit / controller / processor without departing from the broader aspects of the inventive subject matter.

[0101] As in Fig.12 As further shown in FIG. 1 , the drive system control unit 1116 is electrically connected to the drive train 1228 of the vehicle 10, which includes the electric drive system 100, for example, the engine 1106, the generator 1108, the rectifier 1110, the inverters 1112, 1114 and the drive motors 1102, 1104 (such as Fig.11When braking the vehicle 10 in the electric retarder braking mode, the control unit 1116 commands the electric drive system 100 (actually acting as an electric retarder system, which includes the inverters 1112, 1114 and the motors 1102, 1104) to provide the required vehicle retarding torque to the wheels.

[0102] As in Fig.12 Also shown in FIG. 1 , one or both of the drive system control unit 1116 and / or the friction brake control unit 1227 may be configured to receive input from an operator control 1233 (e.g., an ignition switch 1234, an accelerator position sensor 1236, a brake pedal position sensor 1238, and / or a gear selector 1240) for operating the electric motors 1102, 1104 to drive and brake the vehicle 10. The ignition switch 1234 is operable to start and shut down the vehicle. The accelerator position sensor 1236 is configured to detect the position of an accelerator pedal or other actuator. The brake pedal position sensor 1238 is configured to detect the position of a brake pedal or other actuator. The gear selector 1240 provides a tool for allowing an operator to select an intended or desired direction of vehicle movement, such as forward or reverse movement. Additionally or alternatively, the operator control may include another type of input interface 1242, such as a steering wheel or other steering device, a touch screen or other computer interface, a control input from a control system or automatic controller, etc. As Fig.12 As further shown in FIG. 1 , a display 1244 may be electrically connected to the drive system control unit 1116 to allow the operator of the vehicle 10 to view status information related to various vehicle systems. The display 1244 and the operator controls 1233 together form an I / O (input / output) system 1245 .

[0103] Further references Fig.12, the control system 1116 is configured to automate the operation of the vehicle when starting and stopping on a slope in a loaded state. In operation, when the operator of the vehicle (the operator can be a person or an automatic controller) requests the vehicle to stop or the vehicle to move in a certain direction (for example, in both cases, it is performed by operator control), the drive system control unit 1116 communicates with the friction brake control unit 1227 to control the transition from friction brakes to electric power / propulsion, and vice versa. In particular, the control system includes an interface between the drive system control unit 1116 and the friction brake control unit 1227, which allows the drive system control unit 1116 (for example, in response to feedback or other information from the electric drive system 100) to request a specific braking force from the friction brake control unit 1227. This interface also allows the drive system control unit 1116 to request the friction brake unit 1227 to add or remove (i.e., increase or decrease) the friction braking force. As such, in an embodiment, the drive system control unit 1116 is configured to communicate with the friction brake control unit 1227 to control the amount of friction brake application during vehicle stopping and starting. For example, the drive system control unit 1116 may be configured to communicate with the friction brake control unit to at least partially automatically control the amount of friction brake application during vehicle stopping and starting on an inclined grade on which the vehicle is positioned. (At least partially automatically controlling means fully automatically controlling, or automatically controlling in response to and based in part on operator input, e.g., the level or rate of braking or acceleration in response to and proportional to the degree of change in the position of the brake pedal or accelerator pedal.)

[0104] In conjunction with the above, the drive system control unit 1116 is configured to calculate the force required to keep the vehicle on a given incline using system parameters. The drive system control unit 1116 then determines when to release the friction brake or add more friction braking force based on the determined force. The force can be determined based on various methods as outlined in the above-mentioned U.S. patent application No. 14 / 464,226 filed on August 20, 2014. Alternatively or in addition, the control unit 1116 can be configured to determine the force based on information about the incline generated by an onboard inertial measurement unit, vehicle mass information (e.g., determined by a weighing station, or by onboard, physically based calculations of sensor data related to vehicle acceleration under known conditions), other vehicle / system parameters (e.g., wheel radius of the vehicle), etc.

[0105] In an embodiment, the control system 1116 is also configured to provide an anti-slip function. In particular, the drive system control unit 1116 is configured to determine the torque level required to move the vehicle from a stop up the inclined slope (i.e., the vehicle is stopped when on the inclined slope, and then controlled to move up the inclined slope). The torque level can be determined based on the force, for example, the torque level will be at least just above the level of the force. When calculating the required torque (or at some point after calculating the torque), the drive system control unit 1116 communicates with the friction brake control unit 1227 to request the removal of the friction brake application (i.e., the amount of friction brake application = zero) to start the vehicle moving in the desired direction without significant slip. Thus, in an embodiment, the drive system control unit 1116 is further configured to communicate with the friction brake control unit 1227 in response to input from an operator control (for moving the vehicle up or down an inclined slope) to remove the friction brake application and simultaneously control the electric drive system 100 to provide electric power based on a determined torque level for moving the vehicle up (or down) an inclined slope from a stop without noticeable vehicle rollback.

[0106] The drive system control unit 1116 may be configured to communicate with the electric drive system and the friction brake control unit such that the amount and rate at which the friction brake application is removed (by the friction brake control unit controlling the friction brake system) is automatically controlled to be proportional or equal to the amount and rate at which the additional torque is provided (by the electric drive system controlled by the drive system control unit). For example, as the friction brake application is reduced by a specific amount, the torque is increased at least enough to offset the reduced amount of friction brake application to prevent the vehicle from rolling back until the friction brake application is completely removed, at which time the additional torque is generated to move the vehicle forward. (No "significant" vehicle rollback includes no vehicle rollback and vehicle rollback below a threshold that is considered to still meet a specified safety metric, for example, no more than 0.3 meters of rollback for certain haul truck applications.)

[0107] In other embodiments, alternatively or additionally, the control system is configured to provide a controlled stopping function, such as when the vehicle 10 is traveling on a slope. In particular, the drive control unit 1116 is configured to calculate the force required to hold the vehicle on a given inclined slope, and in response to input from an operator control for stopping the vehicle while moving on the slope, communicate with the friction brake control unit 1227 to increase the amount of friction brake application based at least in part on the determined force to stop the vehicle and keep the vehicle stopped on the slope. The drive system control unit 1116 may further be configured to first calculate the force required to stop the vehicle, and simultaneously communicate with the friction brake control unit 1227 to request the amount (and rate) of friction brake application to stop and then hold the vehicle on the inclined slope. Typically, such calculations may take into account vehicle mass, current travel rate / speed, grade inclination, etc. For example, the braking force required to stop the vehicle when traveling up a slope will be based on the vehicle mass and the rate of deceleration (speed change from current speed to zero over a given distance), due to the rolling friction / resistance being less than the factor caused by gravity on the slope. The braking force required to hold the vehicle on the grade will then depend on the mass of the vehicle, the grade, etc., as described above.

[0108] In an embodiment, the application of the friction brake system to stop the vehicle and keep the vehicle stopped on the inclined grade occurs simultaneously with the electric deceleration. Here, the drive control unit 1116 is configured to calculate the force required to keep the vehicle on a given inclined grade, and simultaneously with the reduction of the electric deceleration, communicate with the friction brake controller unit to increase the amount of friction brake application based at least in part on the determined force to stop the vehicle and keep the vehicle stopped on the grade. Thus, as the vehicle moves up the inclined grade, the drive system control unit 1116, in response to input from the operator control for stopping the vehicle, may be configured to first initiate electric deceleration, and as the deceleration force through the electric drive system decreases as the vehicle slows, simultaneously communicate with the friction brake control unit to increase the amount of friction brake application. After the vehicle comes to a complete stop, the amount of electric deceleration may be zero, and in this case, the amount of friction brake application will be sufficient to keep the vehicle stopped on the inclined grade. The drive system control unit 1116 can be configured to automatically control the amount and rate of increase in friction braking application that occurs simultaneously with a reduction in electrical deceleration so that: (i) the overall deceleration profile of the vehicle (speed change over time from a current non-zero speed to zero speed) is linear (and thereby appears smooth to a human operator); and (ii) is proportional in rate to one or more inputs from the operator controls, e.g., the drive system control unit will control a reduction in electrical deceleration while increasing friction braking to provide a faster deceleration in response to an input from the operator controls requesting a higher level / rate of braking relative to an input from the operator controls requesting a lower level / rate of braking.

[0109] In an embodiment, the control system is configured for both a controlled stop of a vehicle on an inclined grade and for preventing rollback when the vehicle is controlled to move forward from its stopped position (e.g., up the grade). Here, the drive control unit, responsive to a first input from an operator control for stopping the vehicle while moving on the grade, is configured to determine a force (to keep the vehicle stopped on the grade) and communicate with a friction brake control unit (e.g., simultaneously with a reduction in electric deceleration) to increase the amount of friction brake application based at least in part on the determined force to stop the vehicle and keep the vehicle stopped on the grade. The drive system control unit is further configured to determine a torque level required to move the vehicle up the grade from stopping. The drive system control unit, responsive to a second input from an operator control for moving the vehicle up the inclined grade, is further configured to: communicate with the friction brake control unit to remove the friction brake application; and simultaneously control the electric drive system to provide electric generating force based on the determined torque level for moving the vehicle from stopping to moving up the inclined grade without significant rollback of the vehicle.

[0110] In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electric generating power to at least the first set of wheels to propel the vehicle and electric deceleration to slow the vehicle. The method further includes, at the drive system control unit, determining a torque level required to move the vehicle from a stop to an upwardly inclined grade. The method further includes, at the drive system control unit, in response to input from an operator control for moving the vehicle up the grade, communicating with a friction brake control unit of the vehicle to remove the application of friction brakes holding the vehicle stopped, and simultaneously controlling the electric drive system of the vehicle to provide electric generating power according to the determined torque level for moving the vehicle from a stop to an upwardly inclined grade without noticeable vehicle rollback.

[0111] In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electric generating force to at least the first set of wheels to propel the vehicle and electrically decelerate to slow the vehicle. The method further includes, at the drive system control unit, determining a force required to maintain the vehicle on an inclined grade on which the vehicle is located. The method further includes, at the drive system control unit, communicating with a brake control unit of the vehicle to reduce or increase an amount of friction brake application applied to at least one of the first set of wheels or the second set of wheels of the vehicle based at least in part on the force determined to maintain the vehicle on the inclined grade.

[0112] In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electric power to at least the first set of wheels to propel the vehicle and electrically decelerate to slow the vehicle. The method also includes, at the drive system control unit, determining the force required to keep the vehicle on an inclined slope on which the vehicle is located. The method also includes, at the drive system control unit, communicating with a brake control unit of the vehicle to reduce or increase the amount of friction brake application applied to at least one of the first set of wheels or the second set of wheels of the vehicle based at least in part on the force determined to keep the vehicle on the inclined slope. The method also includes, at the drive system control unit, receiving an input from an operator control for stopping the vehicle when it is traveling on a slope. A force is determined in response to the received input. The method also includes: at the drive system control unit, communicating with a friction brake control unit to increase the amount of friction brake application based at least in part on the determined force to stop the vehicle and stop the vehicle on the slope.

[0113] In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electric power to at least the first set of wheels to propel the vehicle and electrically decelerate to slow the vehicle. The method also includes, at the drive system control unit, determining a force required to keep the vehicle on an inclined slope on which the vehicle is located. The method also includes, at the drive system control unit, communicating with a brake control unit of the vehicle to reduce or increase the amount of friction brake application applied to at least one of the first set of wheels or the second set of wheels of the vehicle based at least in part on the force determined to keep the vehicle on the inclined slope. The method also includes: at the drive system control unit, receiving an input from an operator control for stopping the vehicle when it is traveling on a slope, wherein the force is determined in response to the received input. The method also includes: at the drive system control unit, communicating with a friction brake control unit while the electrical deceleration is reduced, to increase the amount of friction brake application based at least in part on the determined force to stop the vehicle and stop the vehicle on the slope.

[0114] In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electric power to at least the first set of wheels to propel the vehicle and electrically decelerate to slow the vehicle. The method also includes, at the drive system control unit, determining a force required to maintain the vehicle on an inclined grade on which the vehicle is located. The method also includes, at the drive system control unit, communicating with a brake control unit of the vehicle to reduce or increase an amount of friction brake application applied to at least one of the first set of wheels or the second set of wheels of the vehicle based at least in part on the force determined to maintain the vehicle on the inclined grade. The method also includes, at a drive system control unit: receiving a first input from an operator control for stopping the vehicle while moving on a slope (determining a force in response to the received input); communicating with a friction brake control unit to increase the amount of friction brake application based at least in part on the determined force to stop the vehicle and keep the vehicle stopped on the slope; determining a torque level required to move the vehicle from stop to up the slope; receiving a second input from the operator control for moving the vehicle up the slope; and in response to receiving the second input, communicating with the friction brake control unit to remove the friction brake application and simultaneously controlling the electric drive system to provide electric generating force based on the determined torque level for moving the vehicle from stop to up the inclined slope without noticeable vehicle roll.

[0115] In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electric power to at least the first set of wheels to propel the vehicle and electrically decelerate to slow the vehicle. The method also includes, at the drive system control unit, determining a force required to maintain the vehicle on an inclined grade on which the vehicle is located. The method also includes, at the drive system control unit, communicating with a brake control unit of the vehicle to reduce or increase an amount of friction brake application applied to at least one of the first set of wheels or the second set of wheels of the vehicle based at least in part on the force determined to maintain the vehicle on the inclined grade. The method also includes, at a drive system control unit: receiving a first input from an operator control for stopping a vehicle while moving on a slope (determining a force in response to the received input); communicating with a friction brake control unit to increase the amount of friction brake application based at least in part on the determined force to stop the vehicle and maintain the vehicle stopped on the slope while the electric deceleration is reduced; determining a torque level required to move the vehicle from stop to up the slope; receiving a second input from the operator control for moving the vehicle up the slope; and in response to receiving the second input, communicating with the friction brake control unit to remove the friction brake application and simultaneously controlling the electric drive system to provide electric generating force based on the determined torque level for moving the vehicle from stop to up the inclined slope without noticeable vehicle roll.

[0116] Thus, as should be appreciated, the control system of the present invention helps solve multiple problems associated with vehicle starts and controlled vehicle stops on a grade. In particular, embodiments of the control system can potentially mitigate unsafe vehicle movement during starts on a slope, such as unintentional rolling back on a grade when starting a vehicle run. Moreover, embodiments of the subject matter of the present invention can simplify the driving process for the operator. Typical vehicles require the operator to control three pedals to start and stop safely and smoothly on a grade, while vehicles including the control and braking system of the subject matter of the present invention only require the operator to control a single pedal (or perhaps a brake pedal and an accelerator pedal) because the control system automates the start and stop process through communication and cooperation between the electric drive system and the friction brake system.

[0117] Embodiments of the inventive subject matter also function to avoid rough stops that potentially result in equipment damage, and facilitate controlled stops of the vehicle by automatically controlling the transition from electric retarder braking to friction braking to keep the vehicle on grade. Thus, vehicles including the system are easier to drive and require less specialized skills to operate. Moreover, easier vehicle operation translates into smoother vehicle operation and less wear on components.

[0118] As described above, embodiments of the inventive subject matter may be applicable to relatively large vehicles, such as haul trucks and other vehicles having a gross vehicle operating weight of at least 250 metric tons. However, while the inventive subject matter has been described with particular reference to OHVs and other large vehicles of this type, the inventive subject matter is not intended to be so limited in this regard. In particular, it is contemplated that the inventive subject matter is equally applicable to electric vehicles in general, including, but not limited to, electric off-highway vehicles, automobiles, and the like.

[0119] As described above, the vehicle operator may be a human or an automated controller. Thus, "operator controls" include controls operable by a human and controls (eg, control signals / inputs) associated with a control system / automatic controller.

[0120] In one embodiment, a vehicle control system includes a controller configured to determine a non-zero upper limit for vehicle deceleration. The controller is configured to determine the non-zero upper limit to prevent the vehicle from rolling back along the slope on which the vehicle is traveling upward. The non-zero upper limit for deceleration is determined by the controller based on the load carried by the vehicle, the speed of the vehicle, and the slope of the current upward route of the vehicle. The controller is configured to monitor the deceleration of the vehicle and automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit by controlling the brakes and / or motor of the vehicle. The controller is also configured to activate the brakes and / or supply current to the motor of the vehicle when the vehicle moves upward along the slope at a non-zero speed to prevent the vehicle from rolling back.

[0121] Optionally, the controller is configured to activate the brakes and / or supply current to the motor to prevent the vehicle from rolling backwards while the operator of the vehicle continues to activate the accelerator input device.

[0122] Optionally, the controller is configured to activate the brakes and / or supply current to the motor after the operator releases the accelerator input device of the vehicle to prevent the vehicle from rolling backwards.

[0123] Optionally, the controller is configured to monitor the deceleration of the vehicle when the vehicle moves in the selected direction of travel. The controller is also configured to automatically prevent the deceleration of the vehicle from exceeding a non-zero upper limit by automatically controlling the torque generated by the motor and / or the activation of the vehicle's brakes when the vehicle moves up a slope in the selected direction of travel.

[0124] Optionally, the controller is configured to monitor deceleration of the vehicle and automatically prevent deceleration of the vehicle from exceeding a non-zero upper limit in response to the vehicle travelling upward along a grade of the route, the grade being a non-zero grade.

[0125] Optionally, the controller is configured to automatically prevent deceleration of the vehicle from exceeding a non-zero upper limit in response to the vehicle reaching a zero speed condition and before the vehicle begins to roll backwards down the grade.

[0126] Optionally, the controller is configured to automatically prevent the vehicle from decelerating beyond a non-zero upper limit by activating the vehicle's brakes. The controller may also be configured to subsequently release the brakes and maintain the vehicle's position on the slope by controlling the vehicle's motor and preventing the vehicle from sliding backward down the slope.

[0127] Optionally, the vehicle's motor is powered by alternating current to propel the vehicle, and the controller may be configured to prevent the vehicle from rolling backwards by applying direct current to the motor.

[0128] Optionally, the controller is configured to prevent the vehicle from rolling backwards by applying direct current to the motor without applying the vehicle's brakes.

[0129] Optionally, the controller is configured to prevent the vehicle from rolling backwards by applying direct current to the motor and also applying the vehicle's brakes.

[0130] Optionally, the controller is configured to monitor torque produced by a motor of the vehicle and release the brakes in response to the torque produced by the motor exceeding a threshold torque required to prevent the vehicle from rolling backwards.

[0131] Optionally, the controller is configured to determine the non-zero upper limit in response to a decrease in acceleration of the vehicle.

[0132] Optionally, the controller is configured to determine the non-zero upper limit such that the non-zero upper limit is reduced for heavier vehicle loads, lower vehicle speeds, or steeper grades of the route, and the non-zero upper limit is increased for lighter vehicle loads, faster vehicle speeds, or flatter grades of the route.

[0133] In one embodiment, the method includes determining a non-zero upper limit for the deceleration of the vehicle to prevent the vehicle from rolling backward along the slope on which the vehicle is traveling upward. The non-zero upper limit for the deceleration is determined based on the load carried by the vehicle, the speed of the vehicle, and the slope of the current route of the vehicle. The method also includes monitoring the deceleration of the vehicle and automatically preventing the deceleration of the vehicle from exceeding the non-zero upper limit by controlling the brakes and / or motor of the vehicle. When the vehicle moves upward along the slope at a non-zero speed, the deceleration of the vehicle is prevented from exceeding the non-zero upper limit by activating the brakes and / or supplying current to the motor of the vehicle to prevent the vehicle from rolling backward.

[0134] Optionally, the deceleration of the vehicle is monitored as the vehicle moves in the selected direction of travel. When the vehicle is currently moving up a grade in the selected direction of travel, the deceleration of the vehicle is automatically prevented from exceeding a non-zero upper limit by automatically controlling the torque generated by the motor and / or the activation of the vehicle's brakes.

[0135] Optionally, in response to the vehicle traveling along an upward grade of a route, deceleration of the vehicle is monitored and deceleration of the vehicle is automatically prevented from exceeding a non-zero upper limit, the grade being a non-zero grade.

[0136] Optionally, automatically preventing deceleration of the vehicle beyond a non-zero upper limit occurs in response to the vehicle reaching a zero speed condition and begins before the vehicle begins to roll down the grade.

[0137] Optionally, deceleration of the vehicle beyond the non-zero upper limit is automatically prevented by activating the brakes of the vehicle. The method may also include subsequently releasing the brakes and maintaining the position of the vehicle on the slope by controlling the motor of the vehicle without the vehicle rolling back along the slope.

[0138] Optionally, the vehicle is prevented from rolling backward by applying direct current to the motor, which is an AC motor.

[0139] In one embodiment, a vehicle control system includes a controller configured to determine a selected direction of travel of the vehicle, an operating direction of a motor of the vehicle, and an operating speed of the motor. The controller is configured to identify a backward roll condition of the vehicle in response to the operating direction of the motor of the vehicle being different from the selected direction of travel of the vehicle. The controller is further configured to automatically slow or stop movement of the vehicle by automatically activating a brake of the vehicle in response to the backward roll condition being identified and the operating speed of the motor exceeding a specified non-zero speed threshold.

[0140] Optionally, the controller is configured to identify a cessation of vehicle acceleration in a selected direction of travel, and the controller is configured to automatically slow or stop vehicle movement in response to a rollback condition being identified, the motor operating speed exceeding a speed threshold and a cessation of vehicle acceleration being identified.

[0141] In one embodiment, a vehicle control system includes a controller configured to determine a lower speed limit for the vehicle. The controller is configured to determine the lower limit to prevent the vehicle from rolling backward along a slope that the vehicle is currently traveling up. The lower limit is determined by the controller based on a load carried by the vehicle and the slope of the route the vehicle is currently traveling. The controller is configured to monitor the speed of the vehicle and automatically prevent the vehicle speed from falling below the lower limit by activating the brakes of the vehicle. The controller is configured to activate the brakes based on the speed of the vehicle and independent of the acceleration of the vehicle. The controller is also configured to activate the brakes of the vehicle to prevent the vehicle from rolling backward when the vehicle is moving up the slope at a non-zero speed.

[0142] Optionally, the controller is configured to monitor the speed of the vehicle after the accelerator input device of the vehicle is released, and automatically prevent the speed of the vehicle from falling below a lower limit after the accelerator input device is released.

[0143] Optionally, the controller is configured to monitor the speed of the vehicle while the operator continues to activate or depress an accelerator input device of the vehicle and automatically prevent the speed of the vehicle from falling below a lower limit while the operator continues to activate or depress the accelerator input device.

[0144] In one embodiment, a method includes: receiving a throttle command representing an operator request to increase a throttle setting of the vehicle while brakes of the vehicle are engaged; increasing a torque generated by one or more motors of the vehicle in response to receiving the throttle command; and releasing the brakes of the vehicle in response to one or more of the torque generated by the one or more motors reaching a maximum available torque, the torque generated by the one or more motors reaching a target release acceleration, or expiration of a predetermined non-zero duration.

[0145] In one embodiment, the method includes determining whether the brakes of the vehicle are released when the vehicle is in a stopped state on a grade of a route; in response to determining that the brakes have been released, allowing the vehicle to roll backward down the grade by no more than a specified non-zero threshold distance and / or rapidly accelerating the vehicle using torque generated by one or more motors of the vehicle, and smoothly transitioning the vehicle to movement up the grade by adjusting the torque generated by one or more motors after allowing the vehicle to roll backward down the grade and / or rapidly accelerating the vehicle.

[0146] In one embodiment, the method includes repeatedly determining whether an operator input to release the one or more brakes is received during a blanking interval (when one or more brakes of a vehicle in a stationary position on a grade) , releasing the one or more brakes of the vehicle in response to not receiving the operator input to release the one or more brakes during the blanking interval, and automatically generating torque using one or more motors of the vehicle to propel the vehicle up the grade.

[0147] It should be understood that the above description is illustrative, not restrictive. For example, the above embodiments (and / or their aspects) can be used in combination with each other. In addition, the teachings of the subject matter of the present invention can be modified in many ways to adapt to specific situations or materials without departing from its scope. Although the size and type of materials described in the text are intended to limit the parameters of the subject matter of the present invention, they are not restrictive at all, but exemplary embodiments. After reading the above description, many other embodiments will be obvious to those skilled in the art. As used herein, the terms "including" and "in which" are used as the plain English equivalents of the respective terms "comprising" and "wherein". In addition, the terms "first", "second", "third", "above", "below", "bottom", "top", etc. are only used to distinguish, and are not intended to increase numerical and positional requirements for these objects.

[0148] The above written description uses examples to disclose several embodiments of the inventive subject matter, including the best mode, and also to enable one of ordinary skill in the art to practice embodiments of the inventive subject matter, including making and using any devices or systems and performing any incorporated methods.

[0149] Unless explicitly stated to exclude, as used herein, an element or step enumerated in the singular with the prefix word "one" should be understood not to exclude a plurality of said elements or steps. In addition, reference to "an embodiment" of the subject matter of the present invention is not intended to be interpreted as excluding the existence of additional embodiments that also include the enumerated features. Moreover, unless explicitly stated to the contrary, an embodiment "comprising", "including" or "having" an element or elements having a particular property may include additional such elements without that property.

[0150] As certain changes may be made in the above-described systems and methods without departing from the spirit and scope of the inventive subject matter involved herein, it is intended that all matter described above or shown in the accompanying drawings shall be interpreted merely as illustrating examples of the inventive concepts herein and shall not be understood as limiting the inventive subject matter.

Claims

1. A vehicle control system, comprising: a controller configured to determine a non-zero upper limit for deceleration of the vehicle using a load carried by the vehicle, a speed of the vehicle, and a slope of a route currently traveled by the vehicle, wherein the non-zero upper limit prevents the vehicle from rolling backward along a slope that the vehicle is currently traveling up; wherein the controller is configured to monitor the deceleration of the vehicle, the controller is configured to automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit by controlling the brakes and / or motor of the vehicle, and Wherein, the controller is configured to activate the brake and / or supply current to the motor of the vehicle while the vehicle is still moving in the selected direction of travel to prevent the vehicle from rolling backward while the vehicle is moving up the slope at a non-zero speed.

2. The vehicle control system according to claim 1, wherein: The controller is configured to activate the brake and / or supply current to the motor to prevent the vehicle from rolling backwards while the operator of the vehicle continues to activate the accelerator input device.

3. The vehicle control system according to claim 1, wherein: The controller is configured to activate the brake and / or supply current to the motor to prevent the vehicle from rolling backward after the operator releases the accelerator input device of the vehicle.

4. The vehicle control system according to claim 1, wherein: the controller being configured to monitor the deceleration of the vehicle as the vehicle moves in the selected direction of travel, The controller is also configured to automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit by automatically controlling the torque generated by the motor and / or the activation of the brakes of the vehicle when the vehicle moves up the grade in the selected direction of travel.

5. The vehicle control system according to claim 1, wherein: The controller is configured to monitor the deceleration of the vehicle and automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit in response to the vehicle traveling up the grade of the route, the grade being a non-zero grade.

6. The vehicle control system according to claim 1, wherein: The controller is configured to automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit in response to the vehicle reaching a zero speed condition and before the vehicle begins to roll backwards down the grade.

7. The vehicle control system according to claim 1, wherein: the controller is configured to automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit by activating the brakes of the vehicle, and The controller is configured to subsequently release the brake and maintain the position of the vehicle on the slope by controlling the motor of the vehicle and so that the vehicle does not roll back down the slope.

8. The vehicle control system according to claim 1, wherein: The controller is configured to monitor torque generated by the motor of the vehicle and release the brake in response to the torque generated by the motor exceeding a threshold torque required to prevent the vehicle from rolling backward.

9. The vehicle control system according to claim 1, wherein: The controller is configured to determine the non-zero upper limit in response to a decrease in acceleration of the vehicle.

10. The vehicle control system according to claim 1, wherein: The controller is configured to determine the non-zero upper limit, The heavier the load of the vehicle, the lower the speed of the vehicle or the steeper the slope of the route, the smaller the non-zero upper limit, and The lighter the load of the vehicle, the higher the speed of the vehicle or the gentler the slope of the route, the larger the non-zero upper limit is.

11. A method for controlling a vehicle, comprising: determining a non-zero upper limit for deceleration of the vehicle to prevent the vehicle from rolling backward along a slope on which the vehicle is currently traveling upward, the non-zero upper limit for deceleration being determined based on a load carried by the vehicle, a speed of the vehicle, and a slope of a route currently traveled by the vehicle; monitoring deceleration of the vehicle; and controlling the brakes of the vehicle based on a brake delay time to automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit, wherein the deceleration of the vehicle is prevented from exceeding the non-zero upper limit by controlling the brakes and / or the motor of the vehicle, and wherein control is performed to activate the brakes of the vehicle and / or supply current to the motor of the vehicle to prevent the vehicle from rolling backward while the vehicle moves upward along the slope at a non-zero speed.

12. The method according to claim 11, wherein: monitoring the deceleration of the vehicle as the vehicle moves in a selected direction of travel, and Wherein when the vehicle moves upward along the slope in the selected direction of travel, the deceleration of the vehicle is automatically prevented from exceeding the non-zero upper limit by automatically controlling the activation of the brakes of the vehicle.

13. The method according to claim 11, wherein: In response to the vehicle traveling up the grade of the route, monitoring the deceleration of the vehicle and automatically preventing the deceleration of the vehicle from exceeding the non-zero upper limit, the grade being a non-zero grade.

14. The method according to claim 11, wherein: In response to the vehicle reaching a zero speed condition and before the vehicle begins to roll backward down the grade, the deceleration of the vehicle is automatically prevented from exceeding the non-zero upper limit.

15. The method according to claim 11, wherein: automatically preventing the deceleration of the vehicle from exceeding the non-zero upper limit by activating the brakes of the vehicle, and the method further comprising: The brakes are then released and the position of the vehicle on the slope is maintained by controlling the motor of the vehicle so that the vehicle does not roll back down the slope.

16. A vehicle control system comprising: a controller configured to determine a non-zero lower limit on the speed of the vehicle using a load carried by the vehicle and a slope of a route currently traveled by the vehicle, the controller configured to determine the non-zero lower limit to prevent the vehicle from rolling backward along the slope on which the vehicle is currently traveling; wherein the controller is configured to monitor the speed of the vehicle and automatically prevent the speed of the vehicle from falling below the non-zero lower limit by activating the brakes of the vehicle, the controller being configured to activate the brakes based on the speed of the vehicle and independent of the acceleration of the vehicle, and Wherein, the controller is configured to activate the brake of the vehicle to prevent the vehicle from rolling backward when the vehicle moves upward along the slope at a non-zero speed.

17. The vehicle control system according to claim 16, wherein: The controller is configured to monitor the speed of the vehicle after an accelerator input device of the vehicle is released, and The speed of the vehicle is automatically prevented from falling below the lower limit after the accelerator input device is released.

18. The vehicle control system according to claim 16, wherein: The controller is configured to monitor the speed of the vehicle as the operator continues to activate or depress an accelerator input device of the vehicle, and The speed of the vehicle is automatically prevented from falling below the non-zero lower limit while the operator continues to activate or depress the accelerator input device.

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