Lifting device and gradient control method
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TEREX SOUTH DAKOTA INC
- Filing Date
- 2021-12-29
- Publication Date
- 2026-08-03
Smart Images
Figure 0007899310000001 
Figure 0007899310000002 
Figure 0007899310000003
Abstract
Description
Technical Field
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[0005]
[0001] [Cross - Reference to Related Applications] This application claims the priority of U.S. Application Serial No. 17 / 475,788, filed on September 15, 2021, the disclosure of which is hereby incorporated by reference in its entirety.
[0002] Various embodiments relate to a lift device or utility vehicle having an electric drive train and to the control of the lift device on a slope.
Background Art
[0003] A lift device with an electric drive system may use regenerative braking from a traction motor to charge a traction battery. When the lift device is traveling downhill over a slope, the traction motor may provide braking to decelerate the vehicle. Since the traction motor has a related braking torque limit, depending on the speed and slope of the lift device, the traction motor may not be able to control the vehicle to the commanded speed, whereby the vehicle speed may increase beyond the required or commanded speed, or the parking brake may be suddenly set.
Summary of the Invention
[0004] In one embodiment, a lift device is provided that includes a chassis, a lift mechanism that supports a lift platform relative to the chassis, and a plurality of traction devices that support the chassis on a base surface. An electric motor is drivingly coupled to at least one of the plurality of traction devices, and a traction battery is electrically connected to the electric motor. A user input unit is provided to control the speed of the lift device by inputting a requested speed. A controller is configured to output a braking torque to the electric motor and command power to be supplied to the traction battery in response to the lift device being on a non - zero slope and the requested speed being greater than a predetermined speed, so as to limit the speed of the lift device to the predetermined speed.
[0005] In another embodiment, a method for controlling a lift device is provided. A requested speed for the lift device is received from a user input unit. The lift device is propelled at the requested speed via electric motors connected to wheels, which are electrically connected to a towing battery. The requested speed is determined to be greater than a predetermined speed when the lift device is on a slope, and the predetermined speed depends on the slope. The speed of the lift device is limited to the predetermined speed by commanding the electric motors to output braking torque and supply power to the towing battery while the lift device is on a slope. If the speed of the lift device exceeds the predetermined speed while on a slope, the parking brake is commanded to be activated to stop the lift device.
[0006] In one embodiment, a propulsion system is provided comprising an electric motor adapted to be coupled to at least one wheel, a traction battery electrically connected to the electric motor, and a user input unit that controls the speed of at least one wheel by inputting a requested speed. The controller is configured to respond when the system is on a non-zero gradient and the requested speed is greater than a predetermined speed by commanding the electric motor to output braking torque and supply power to the traction battery, thereby limiting the speed of the system to the predetermined speed. [Brief explanation of the drawing]
[0007] [Figure 1] Figure 1 is a perspective view of a lift device according to the first embodiment.
[0008] [Figure 2] Figure 2 is a perspective view of a lift device according to the second embodiment.
[0009] [Figure 3] Figure 3 is a schematic diagram of the lifting device shown in Figure 1 or Figure 2.
[0010] [Figure 4] Figure 4 is a hydraulic circuit diagram of the lifting device shown in Figure 1 or Figure 2.
[0011] [Figure 5] Figure 5 is a flowchart showing the control method of the lift device according to the embodiment. [Modes for carrying out the invention]
[0012] Where necessary, detailed embodiments of the present invention are disclosed herein, but it should be understood that the disclosed embodiments are merely illustrative examples of the present invention, which can be embodied in various alternative forms. The figures are not necessarily to scale, and some features may be exaggerated or minimized to illustrate the details of certain components. Accordingly, certain structural and functional details disclosed herein should not be construed as limiting, but merely as representative grounds to teach those skilled in the art how to employ the present invention in various ways.
[0013] Figure 1 shows a lifting device 10 or utility vehicle 10 for use with the present disclosure according to a first embodiment. The lifting device or utility vehicle is used in a commercial or industrial environment and may include lifting devices including portable material lifts, aerial work platforms, telehandlers, scissor lifts, rough terrain telescopic load handlers, and telescopic / articulated booms. In Figure 1, the lifting device 10 is illustrated as a telescopic boom according to a non-limiting embodiment.
[0014] The lifting device 10 has an electric propulsion system for propelling the vehicle, as will be described later with respect to Figure 3. The lifting device 10 also has an electric or hybrid hydraulic system for operating the lifting platform and other vehicle systems such as steering, which will be described below with respect to Figure 4. Alternatively, the working functions may be electrically operated, for example, without using a hydraulic system or circuit.
[0015] The lifting device 10 has a base 12 or chassis 12 supported on a foundation terrain by a plurality of towing devices 14, such as four wheels 14. The lifting device 10 is configured to lift loads such as people, tools, and cargo against a supporting surface 16 or foundation terrain, such as paved or unpaved ground, roads, aprons such as sidewalks or parking lots, interior or exterior floors of structures, or other surfaces.
[0016] The lifting device 10 includes a vehicle lift component 18 such as a platform, a base or chassis 12, and a support assembly 20 connecting the platform 18 and the base 12. The base 12 is supported on a support surface 16 by a towing device 14 such as wheels. The towing device 14 may include tires and / or tracks. The vehicle 10 has a first axle 24 having two wheels 14 and a second axle 26 having another two wheels 14. The axle 24 may be a front axle, and the axle 26 may be a rear axle. In other embodiments, the vehicle 10 may have two or more axles. In other embodiments, the towing device 14 may be aligned with each other along the transverse axis of the vehicle, but may not have axles 24, 26 extending between them.
[0017] The support assembly 20 may include one or more actuators, such as hydraulic actuators as described below, along with other structural members, to provide a lifting mechanism for the platform 18.
[0018] The base 12 has first and second opposing sides or ends 30, 32 corresponding to the front and rear ends of the base and the vehicle, respectively. The vehicle 10 is configured to move in either direction along the longitudinal axis 40 of the vehicle, for example, depending on the direction in which the wheels 22 rotate.
[0019] The operator of the lift device 10 inputs commands to the lift device, for example, via the operator input unit or user input unit 50 on the control panel. The operator input unit 50 may include a joystick for inputting speed and direction commands for the lift device 10. For example, moving the joystick forward relative to the neutral center position gives a forward speed command for the vehicle, and the vehicle moves forward at a selected speed, for example, to the left in Figure 1. Moving the joystick in the opposite direction relative to the neutral position gives the vehicle a reverse speed command, and the vehicle moves backward or in the reverse direction, for example, to the right in Figure 1, at a selected speed. The magnitude of the speed command is based on the distance between the actual joystick position and the neutral center position.
[0020] The control panel 50 may further have an operator input for selecting a speed mode of the device 10. In one embodiment, the lift device 10 has three speed modes, each speed mode having a different maximum speed for the lift device. The first speed mode has the highest maximum speed and is used when the lift platform is retracted; the second speed mode has a lower maximum speed and is also used when the lift platform is retracted; and the third speed mode has the lowest maximum speed and is used when the lift platform is deployed from the retracted position. The joystick can be recalibrated based on the mode so that the entire forward position of the joystick provides the maximum speed allowed in that mode, and similarly the entire backward position.
[0021] In one example, in the first speed mode, the speed of vehicle 10 ranges from zero to 20 miles per hour in either direction; in the second speed mode, the vehicle speed ranges from zero to 5 miles per hour in either direction; and in the third speed mode, the vehicle speed ranges from zero to 2 miles per hour in either direction. In another example, in the first speed mode, vehicle speeds ranging from zero to 4 miles per hour in either direction are possible; in the second speed mode, vehicle speeds ranging from zero to 2 miles per hour in either direction are possible; and in the third speed mode, vehicle speeds ranging from zero to less than 1 mile per hour in either direction are possible.
[0022] The system controller can further select the speed mode of the device based on the operating conditions and can override the operator's selection via the input unit 50.
[0023] The control panel 50 also provides other operator input parts for controlling the position of the lift part 18 relative to the base 12. Further, the control panel 50 can include a display screen, indicator lights, etc. to provide information about the lift device 10 to the operator.
[0024] FIG. 2 shows a lift device 10 for use with the present disclosure according to another embodiment. Elements that are the same as or similar to those described above with respect to FIG. 1 are given the same reference numbers for simplicity. In FIG. 2, the lift device 10 is illustrated as a scissor lift according to another non-limiting example.
[0025] FIG. 3 is a schematic view of the lift device 10 of FIG. 1 or FIG. 2, or another lift device such as a forklift. Elements that are the same as or similar to those described above with respect to FIG. 1 are given the same reference numbers for simplicity.
[0026] The lifting device 10 has a plurality of towing devices 14. In one embodiment, the towing devices 14 are provided by wheels, and the lifting device 10 has four wheels, as shown above with respect to Figures 1 and 2. In other embodiments, the lifting device 10 may have four or more wheels.
[0027] The lifting device 10 has an electric propulsion system 60. The electric propulsion system 60 includes one or more electric motors 62 that are driven and connected to at least one of a plurality of traction devices 14 and propel the lifting device on the base terrain. In one embodiment, the electric motors 62 are provided as hub motors for two or more wheels 14. In a further embodiment, as shown, the electric propulsion system 60 has four electric motors 62 provided as hub motors for four wheels 14. In other examples, the electric motors 62 may be connected to two or more wheels, for example, via a differential in the driveline. Alternatively, only a portion of the wheels 14 provide traction to the vehicle, for example, as two-wheel drive.
[0028] Each electric motor 62 is connected to the traction battery 64 via an associated motor controller 66. The motor controller 66 controls the speed and torque of each electric motor 62, and the motors 62 may be controlled independently. The motor controller 66 is shown as a single integrated element, but may be provided as a separate element for each motor 62. The voltage of the motor controller 66 may be equivalent to the voltage of the traction battery 64. The motor controller 66 has associated voltage limits. Each of the motor controllers 66 communicates with the system controller 68. Operator input units such as the control panel 50 and joystick also communicate with the system controller 68.
[0029] The traction battery 64 may be provided by one or more cells, which may be wet or dry cells, and may be formed from a lead oxide cell, a lithium-based chemical cell, or other chemical cell. The traction battery 64 may have associated voltage limits, current limits, charge state limits, or temperature limits. In a non-limiting example, the motor controller 66 has a voltage limit. In another example, with a lithium chemical cell, the battery 64 may have voltage and current limits, as well as operating temperature limits. For example, the battery 64 may have limitations on charging when outside its temperature range, for example, after a cold start when the ambient temperature is low, and the motor controller 66 and / or system controller 68 may limit the charging of the battery under such conditions.
[0030] The system controller 68 communicates with various propulsion and hydraulic components and sensors to control the device 10. The controller 68 may provide or be part of a vehicle system controller (VSC), may include any number of controllers, may be integrated into a single controller, or may have various modules. Some or all of the controllers may be connected by a controller area network (CAN) or other system. The controllers may also be connected to random access memory or other data storage systems.
[0031] In various embodiments, the apparatus 10 is supported by a chassis 12 and has a sensor 72 that communicates with a controller 68. The sensor 72 may be used, for example, to determine the tilt of the apparatus 10 while stationary in order to limit the deployment of the lift platform based on inclination or gradient. The sensor 72 may be an electronic tilt sensor provided by a multi-axis accelerometer that reports pitch and roll angles or horizontal acceleration vectors to the controller 68. The multi-axis accelerometer 72 may include a solid-state accelerometer to estimate the tilt of the chassis 12 and the apparatus 10.
[0032] In another example, sensor 72 is a multi-axis inertial sensor that can measure and report the true slope or gradient to the controller.
[0033] The motor controller 66 may control the electric motor 62 in a speed control feedback loop based on speed input from the operator. For example, the operator can input a selected speed via the joystick 50, and the motor controller 66 can control or modulate the torque of the electric motor 62 to provide a desired speed output based on the operator's request. Thus, in order to reduce the speed of the traction motor 62, the motor controller 66 can command the traction motor to output a reduced torque or a torque in the opposite direction to the motor rotation, for example, as a braking torque. The traction motor 62 may be provided as a four-quadrant motor controllable between forward braking, forward motoring, reverse motoring, and reverse braking.
[0034] Furthermore, the towing battery 64 can be charged externally, for example, via an electrical input from an external power source such as a charging station.
[0035] Each electric motor 62 may be controlled to rotate in a first and a second direction, and furthermore, its speed and torque output may be controlled. Thus, the electric motors 62 can propel the vehicle across lower terrain with a positive torque output. The electric motors 62 can also function as generators, providing a negative torque output to brake or decelerate the vehicle and supply power to the traction battery 64.
[0036] In the illustrated example, the lifting device 10 is provided without a service brake system. Thus, the electric motor 62 is the only device that applies braking force to the wheels 14 to control the vehicle speed while it is in motion. A service brake system is conventionally provided by drum brakes, disc brakes, etc., and provides controlled brake input by the operator, for example, to slow the vehicle down to a low speed.
[0037] In the illustrated example, the lift device 10 is equipped with a parking brake system. In the parking brake system, a parking brake 70 is provided on each wheel 14. In one non-limiting embodiment, the parking brake 70 may be integrated with the traction motor 62 and the wheel 14 drive assembly and may be provided as a spring-applied, coil-release brake, or, for example, a disc brake. The controller 68 or operator can actuate the parking brake 70 to stop the lift device 10, or release the parking brake 70 to allow the lift device 10 to move relative to the terrain of the foundation. When the parking brake 70 is actuated or set while the device 10 is moving, the wheels 14 will not rotate and the lift device 10 will slide and stop.
[0038] In the electric propulsion lift device 10 as described above with respect to Figures 1-3, the traction motor 62 can provide both propulsion torque and braking torque in both forward and reverse directions. When these motors 62 are using positive torque to move the device forward, the traction battery 64 is discharged to supply power. When these traction motors 62 are braking to decelerate the vehicle, the direction of the battery current is reversed, and the braking power charges the battery 64, for example, by regenerative braking.
[0039] For example, charging via regenerative braking causes the voltage of the traction battery 64 to rise. Depending on the size and chemical properties of the battery 64, as well as the braking power applied, the voltage of the battery 64 may rise significantly. While this voltage rise may be temporary, the motor controller 66, traction battery 64, and / or other on-board power electronics devices may have associated voltage or current limits. For example, the three-phase motor controller 66 may have associated voltage thresholds, and when these thresholds are reached, the torque of the motor 62 during braking may be limited. This, in turn, may limit the traction motor 62's ability to brake and control the speed of the vehicle 10, for example, on a gradient, potentially resulting in unintended acceleration downhill and / or lift device speeds exceeding the requested or commanded speed of the device 10. The method described below with respect to Figure 5 provides control of the lift device 10 during such scenarios.
[0040] Figure 4 is a hydraulic circuit diagram of the lift device 10 of Figure 1 or Figure 2 according to an embodiment, where the device includes a hydraulic system 80. The hydraulic system 80 may be a hydraulic circuit with a closed-loop system or an open-loop system. In the illustrated example, the hydraulic system includes two pumps 82, 84, with the second pump 84 piggybacking on the first pump 82. Alternatively, a single pump housing may be provided, and the housing may be divided to provide the volume for the two pumps 82, 84. The first and second pumps 82, 84 are driven by a pump motor 86, which is an electric motor electrically connected to the traction battery 64 described above with reference to Figure 3, via a pump motor controller 88. The speed of the pump motor 86 may be controlled to control the flow rate from the pumps 82, 84. As used herein, the flow rate from the pumps 82, 84 may be controlled by controlling the speed and / or displacement from the pumps, or via pump valves 90, 92.
[0041] In an alternative example, the hydraulic system may have a single pump, such as pump 82, which is driven by a pump motor.
[0042] Pumps 82, 84 may be provided as variable displacement pumps. Alternatively, as shown in the figure, each pump 82, 84 may have associated pump valves 90, 92 that fluidly connect the associated pump to the pressure galley 100 or to the return line 102 and tank 104. Thus, the displacement or flow to the pressure galley 100 can be controlled by selectively controlling the first and / or second pump valves 90, 92 to supply flow to the pressure galley 100. The displacement or flow rate to the pressure galley 100 can be further controlled within the range provided by the pump valves 90, 92 at selected positions by selectively controlling the speed of the pump motor 86.
[0043] In various embodiments, and as illustrated, the hydraulic system 80 further comprises an internal combustion engine 110, such as a diesel or gasoline engine, which is coupled to a pump motor 86 via an overrunning clutch 112. Thus, the pump motor 86 is positioned between the engine 110 and pumps 82, 84. The engine 110 and / or pump motor 86 can be actuated to drive pumps 82, 84. The overrunning clutch 112 engages the engine 110 and the pump motor 86 to mechanically couple them together when the rotational speed of the output shaft of the engine 110 is less than or equal to the rotational speed of the shaft of the pump motor 86. Thus, when the overrunning clutch 112 is disengaged, the pump motor 86 acts independently of the engine 110 when the rotational speed of the pump motor is greater than the rotational speed of the engine.
[0044] In other embodiments, the hydraulic system 80 may be electrically powered only, without an engine or overrunning clutch, and with only the pump motor 86 rotating the pump.
[0045] The engine 110, the pump motor controller 88, and the selected valve also communicate with the vehicle controller 68.
[0046] The first and second pumps 82 and 84 supply a pressurized fluid flow to the pressure galley 100. The hydraulic functions 120 of the lifting device 10 are connected to the pressure galley 100 and receive pressurized fluid from there, for example, via a valve 122. For example, hydraulic actuators 124 for the support assemblies of the lifting platform, wheel steering, axle control, and other device functions are fluidly connected to the pressure galley 100. The hydraulic actuators 124 are also coupled to a return line 102 downstream of the pressure galley 100 and actuators 124. The return line 102 provides a fluid path from the pressure galley 100 and actuators 124 to the tank 104 and pumps 82 and 84. Although only two hydraulic actuators 124 are shown, any number of hydraulic actuators are conceivable for use with the hydraulic system 80.
[0047] A valve 130, such as a relief valve, is positioned between the pressure galley 100 and the return line 102, allowing the pressure galley to be directly connected to the return line. The valve 130 may be a variable-position valve, for example, as a proportional or inversely proportional relief valve. In other examples, the valve 130 may be a fixed-position relief valve. The position of the valve 130 can be controlled via a solenoid communicating with a system controller 68. The position of the valve 130 may be controlled to control the pressure in the pressure galley 100. When the valve 130 is open, the flow from pumps 82, 84 and the pressure galley 100 flows into the return line 102, bypassing the actuator 124, and the pressure in the pressure galley 100 is minimized. When the valve 130 is closed, all the flow from pumps 82, 84 is directed to the pressure galley 100, and the pressure in the pressure galley 100 is maximized. The position of the valve 130 can be controlled or adjusted between an open position, a closed position, and a partially open position to control the pressure in the pressure galley 100.
[0048] The hydraulic system 80 may have other components not shown, including other valves, actuators, filters, etc.
[0049] The hydraulic system 80 may be used to draw power from the battery 64 while the lifting device 10 is braking via the electric motor 62, and when voltages or other parameters related to the motor control device 66, the traction battery 64, or other power electronic devices are approaching their thresholds or limits in accordance with this disclosure. As the flow rate from the pumps 82, 84 increases and / or the pressure in the system 80 increases, the power consumption by the hydraulic system 80 also increases. For example, when high-pressure fluid is metered via the relief valve 130, the power is dissipated into the fluid as heat. This disclosure provides control over the speed and / or displacement of the pumps 82, 84, as well as control over the position of the valve 130, so that the amount of power dissipated by the hydraulic system 80 can be controlled as described below with respect to Figure 5 to maintain the operation of the lifting device 10 within electrical limits and to charge the traction battery 64 within a rechargeable range.
[0050] Figure 5 shows a method 200 for controlling a lift device such as the lift device 10 shown above with respect to Figures 1-4. In various embodiments, the steps of method 200 may be performed in different orders, in parallel or in series, and / or may be added or omitted. Method 200 may be performed on the device 10, for example, via a controller 68.
[0051] Various embodiments of Method 200 have relevant, non-limiting advantages. For example, Method 200 and the device 10 control the vehicle speed when the device 10 is traveling on a non-zero gradient or downhill gradient, limiting the speed increase or acceleration of the device when traveling on a gradient, and preventing or delaying the engagement of the parking brake 70 and the sudden stop of the device 10, especially when traveling at high speeds.
[0052] As described above, while the device 10 is traveling on a non-zero gradient, the traction motor 62 may need to function as a generator and provide braking torque to control the speed of the device 10. As used herein, a non-zero gradient or gradient refers to a ground that has a non-zero angle relative to inclined terrain or horizontal or flat terrain. This may be particularly true while the device 10 is descending a slope, as there is no service brake to control or reduce the vehicle speed. The electric motor 62 converts the torque and speed of the wheels into electricity. At high speeds, steep gradients, and rapid deceleration of the lift device 10, the braking force required to maintain vehicle speed or prevent acceleration may be greater than the braking torque available from the traction motor 62. The braking force of the electric motor 62 may depend on the speed of the motor 62 and the voltage of the battery 64. The torque that the motor 62 can generate is controlled or limited by its torque-speed curve. In this scenario, the device may accelerate down the gradient or exceed the commanded speed. Furthermore, although this is a non-limiting example, the motor 62 has a torque curve that provides high torque at low speeds and low torque at high speeds, which may further limit the braking of the motor 62 when descending a gradient.
[0053] Furthermore, the braking torque generated by the traction motor 62 may be greater than thresholds or limits associated with the battery 64, motor controller 66, or other electrical components. The motor controller 66 may limit regenerative braking when the voltage, charge state, or other parameters of the traction battery 64 are close to thresholds for protecting the battery 64 and / or the motor controller 66, and therefore, braking by the electric motor 62 may be limited under certain circumstances of the lift device 10. Similarly, if the device 10 has a lithium chemical traction battery 64, the battery may have associated current and / or voltage thresholds.
[0054] Since the lift device 10 does not have a service brake, the controller 68 must set the parking brake 70 if the device 10 is accelerating or exceeds the commanded speed or another upper speed threshold, which provides a sudden stop for the device and affects drivability.
[0055] This disclosure provides a device 10 for descending a slope and a method 200 for controlling the device 10. The method 200 controls the device 10 so that the braking force of the motor 62 does not exceed any limit set by the motor 62 or the battery 64 when the device is descending a slope or incline. The method 200 reduces the travel speed of the device 10 before encountering a situation that would result in high braking force, or braking force at or near the upper limit, for example, before the speed of the device 10 rises above a commanded or requested speed due to vehicle acceleration and increasing gradient. Such high braking force requirements may occur when making a sudden stop from high speed on a steep gradient. Therefore, the drive speed of the device 10 is reduced when traveling down a slope with the torque of the motor 62 required to maintain speed on the gradient limited to a low motor speed.
[0056] By reducing the speed of the vehicle 10, the motor 62 can be operated at a point on the torque curve where it can generate sufficient torque to control the speed of the device 10. If the motor 62 cannot generate sufficient braking torque, the device 10 may exceed the commanded speed when descending a slope. Method 200 estimates or determines the slope and reduces the speed of the device 10 before the slope becomes too steep and the motor 62 loses control of the speed.
[0057] Method 200 begins in step 202, where it is determined whether the device 10 is operating. In step 204, the controller 68 determines whether the speed of the device 10 is greater than a threshold, or whether the rotational speed of the traction motor 62 is greater than a threshold.
[0058] In step 206, method 200 determines whether the device 10 is on a slope or on a downhill slope. The controller 68 can estimate the slope based on sensors mounted on the device 10 or via signals received by the controller 68 from the motor controller 66. According to various embodiments, the controller 68 can determine or estimate the slope as described below. In step 206, the controller 68 determines that the device is on a slope and further determines that the device is moving downhill or in a downhill direction. Furthermore, in some examples, the slope is greater than the threshold slope for method 200 to proceed to step 208.
[0059] In a non-limiting example, the controller 68 infers that the lift device 10 is on a slope based on the fact that the output torque of the electric motor 62 is applied in the opposite direction to the rotational speed of the electric motor 62. The controller may further infer that the device 10 is on a slope if the output torque of the electric motor 62 is greater than a predetermined torque value, or if the rotational speed of the motor 62 or the requested rotational speed is greater than or equal to a predetermined rotational speed. For example, the controller 68 may implement predetermined limits, such as those described in step 208 below, in response to the motor speed and braking torque being greater than or equal to thresholds, respectively. The braking torque of the motor 62 is proportional to the slope angle. Therefore, the controller 68 may be further configured to infer the slope, for example, the value of the slope, as being proportional to the output torque of the electric motor 62. The controller 68 may receive a signal from the torque sensor of the motor 62, or instead may infer the torque of the motor 62, for example, based on a lookup table, or by determining the torque from other motor parameters such as speed, voltage, current, and temperature supplied by the motor controller 66.
[0060] In another, less restrictive example, the controller 68 receives signals from a multi-axis accelerometer 72 supported by the chassis 12, such as a mass-based multi-axis accelerometer 72. The controller 68 could directly estimate the gradient using the signals from the multi-axis accelerometer 72, but the estimated gradient may be inaccurate because the signals from the sensor 72 include acceleration components when the device 10 is moving.
[0061] In another non-limiting example, the controller 68 receives a signal from a multi-axis accelerometer 72 supported by the chassis 12, such as a mass-based multi-axis accelerometer 72, and corrects the signal to estimate the gradient. In one example, the controller 68 corrects the signal to estimate the gradient by removing the acceleration component from the signal, the acceleration component being based on a change in the rotational speed of one of the traction devices. The signal from the multi-axis accelerometer 72 includes both the tilt of the device 10 indicating the gradient and components of acceleration or deceleration resulting from the movement of the device 10 when the device 10 is driven or operated. The signal from the sensor 72 may be corrected to estimate the gradient by removing the acceleration vector component from the signal that determines the tilt and gradient of the vehicle. The acceleration vector component may be determined by taking the derivative of the velocity of the wheels 14 to determine the vehicle acceleration. The vehicle acceleration vector in the direction of travel is subtracted from the gravity gradient vector of the tilt sensor signal to produce a corrected gradient vector. The corrected signal or corrected gradient vector indicating the gradient can be used to reduce the speed of the device 10, as described below.
[0062] In yet another non-limiting example, the controller 68 receives signals from a multi-axis accelerometer, such as a mass-based multi-axis accelerometer 72 supported by the chassis 12, and estimates the gradient by applying a filter to the signals. In one embodiment, the controller 68 applies a filter that is modulated based on the acceleration component determined from the change in rotational speed of one of the traction devices 14. For example, the signal filter may be variable to remove the effects of acceleration and deceleration from the sensor 72 signal so that the filtered vehicle tilt signal is less affected by vehicle acceleration, and is used to estimate the gradient. In a further example, the controller 68 applies an exponential filter, the time constant of the filter depends on the acceleration component determined from the change in rotational speed of one of the traction devices 14. The exponential filter may, in one example, be a signal exponential filter.
[0063] As described above, the measurement of the tilt or gradient of the device 10 using the mass-based multi-axis acceleration sensor 72 is affected by a bias caused by angular acceleration when the device 10 is in motion. Angular acceleration includes components of both longitudinal and lateral acceleration. When the vehicle 10 accelerates, the sensor 72 simultaneously detects both changing linear velocity and angular velocity, with the linear velocity changing faster than the angular velocity. However, the chassis 12 of the vehicle 10 cannot rotate at the high speed induced by the linear acceleration of the wheels 14. A filter is applied to the signal to remove the component attributable to linear velocity or linear acceleration from the overall velocity, leaving angular velocity and velocity in the filtered signal. The rotational speed attributable to the gradient of the device 10 can be determined from the filtered signal, thereby allowing the controller 68 to infer the gradient.
[0064] In the signal, the bandwidth of angular acceleration is lower than that of linear acceleration. Therefore, the signal filter is modulated by the controller 68 to remove high-frequency linear acceleration components from the signal when the vehicle 10 is accelerating. The filter modulation is based on a linear acceleration rate that can be determined from the wheels 14, or a linear acceleration rate that can be determined from the rate of change of the accelerometer. In an unrestricted example, the filter is a single exponential filter with a time constant modulated by the controller 68 as a function of longitudinal chassis acceleration determined from the wheel sensors or traction motor, so that the filter is a dynamic filter. Furthermore, the time constant may vary as a function of longitudinal chassis acceleration between two limits, and may vary linearly or nonlinearly between the two limits. In another unrestricted example, the filter is a double exponential filter with two time constants.
[0065] In another example, the controller 68 uses a mass-based multi-axis accelerometer 72 to receive a signal having data related to the pitch or gradient angle of the device 10, and then reduces the drive speed in step 208 when the gradient angle approaches a predetermined gradient or gradient angle related to the torque limit of the electric motor 62 at the current speed of the motor 62. Furthermore, the controller 68 may further condition the signal from the sensor 72 to reduce or prevent, for example, speed limiting events of the motor 62 related to hysteresis. Signal conditioning by the controller 68 may include, for example, variable time averaging of the signal based on the acceleration of the device 10. Signal conditioning may additionally or alternatively include the controller 68 measuring the acceleration vector of the vehicle 10 in the direction of travel in order to correct the sensor vector by generating a corrected gradient vector by subtracting the measured vehicle acceleration vector from the gravity gradient vector.
[0066] In a further non-limiting example, the controller 68 receives signals from a multi-inertial sensor supported by the chassis 12, and the signals from the sensors indicate a gradient.
[0067] In step 208, if the actual or requested speed is greater than a predetermined speed, and while the vehicle is descending the gradient determined in step 206, the controller 68 limits the speed of the lift device 10 to a predetermined speed in response. The controller 68 may also enforce the predetermined speed limit via the speed control loop of the motor 62. The controller 68 can command the traction motor 62 to output braking torque and supply power to the traction battery 64 to limit or reduce the vehicle speed. A lower motor braking torque is required to decelerate or stop the vehicle by reducing the vehicle speed to a predetermined speed, and therefore the motor 62 has a larger torque bandwidth to control the vehicle speed before reaching the motor 62's upper torque limit or power limit.
[0068] The predetermined speed may depend on or be based on the gradient determined in step 206. In one example, the predetermined speed is a function of the gradient. In a further example, the predetermined speed decreases as the gradient increases. For example, different gradient ranges may have associated predetermined speeds or speed zones, such that a gradient from zero to 10 percent has a predetermined speed that is 100% of the maximum speed for the selected mode, a gradient from 10 to 20 percent has a predetermined speed that is 50% of the maximum speed for the selected mode, and a gradient above 20 percent has a predetermined speed that is 20% of the maximum speed for the selected mode. In another example, the gradient range may have associated predetermined speeds set, for example, a gradient from zero to 10 percent with a predetermined speed that is 100% of the maximum speed for the selected mode, a gradient from 10 to 20 percent with a predetermined speed of 5 miles per hour, and a gradient above 20 percent with a predetermined speed of 2 miles per hour. In other examples, other gradient percentage ranges or predetermined speeds or percentages may be used. In a further example, a predetermined speed is calculated from a function or lookup table that takes the gradient as input, and the predetermined speed changes continuously according to the gradient.
[0069] Furthermore, in step 208, the lift device 10 may move at a speed lower than the predetermined speed. The controller 68 may recalibrate the speed associated with the endpoints of the joystick 50, for example, the full forward position and the reverse position, so that the speed is predetermined in each direction. The speed curve or requirements are similarly recalibrated between the neutral position and the endpoints of the joystick 50. Thus, the vehicle 10 may be driven at a speed below the predetermined speed based on the position of the joystick 50 between the neutral position and the position between full forward or full reverse.
[0070] In step 210, the controller 68 monitors battery parameters, which may include the voltage of the motor controller 66, the voltage of the battery 64, the charge state of the battery 64, the temperature of the battery 64, or other parameters related to the power electronics device.
[0071] While the electric motor 62 is outputting braking torque and supplying power to the towing battery 64, in response to the battery parameters being outside a predetermined range, the controller 68 activates the hydraulic system 80 in step 212 by increasing the flow rates of pumps 82, 84 and / or controlling valve 130 to decrease the valve opening size, thereby increasing the pressure in the pressure galley 100 and reducing the power to the towing battery 64. The flow rates of pumps 82, 84 and valve 130 may be controlled sequentially or simultaneously.
[0072] By increasing the flow rate of pumps 82 and 84, the pump motor 86 consumes power from the traction battery 64, resulting in a decrease in power from the traction motor 62 to the traction battery 64, which in turn allows the traction motor 62 and motor controller 66 to continue generating braking torque and replace the current being discharged to the hydraulic system 80.
[0073] Similarly, reducing the size of the opening of valve 130 to increase the pressure in the pressure galley 100 also reduces the power supplied to the towing battery 64, thereby reducing the power supplied to the towing battery 64 by supplying high pressure to the pressure galley 100 and dissipating energy as heat across the relief valve 130, and consequently reducing the power supplied to the towing battery 64 from the towing motor 62, allowing the towing motor 62 and motor controller 66 to continue generating braking torque and replace the current discharged to the hydraulic system 80.
[0074] It should be noted that steps 210 and 212 are optional and may be performed on lift devices equipped with the associated hydraulic system 80. Steps 210 and 212 are omitted on lift devices without the hydraulic system 80, and may also be omitted on vehicles with the hydraulic system, depending on the range of anticipated vehicle operating conditions and battery parameters.
[0075] In step 216, the controller 68 is configured to command the parking brake 70 to stop the lift device 10 in response to the braking torque from the traction motor 62 being insufficient to maintain the lift device 10 below a predetermined speed while the lift device 10 is on a slope in step 214. The controller 68 determines whether the traction motor 62 has a sufficient torque bandwidth to control the speed of the device 10 to a predetermined limit. The controller 68 may set the parking brake 70 in response to the voltage of the motor controller 66 being above a threshold voltage and the speed of the lift device 10 being above a predetermined speed while the electric motor 62 is outputting braking torque. Alternatively, the controller may set the parking brake 70 in response to the braking torque of the electric motor 62 being above a threshold, the threshold depending on the upper torque limit of the traction motor. In a further example, the controller 68 may set the parking brake in response to the speed of the motor 62 being greater than a predetermined speed, for example, greater than an offset above a predetermined speed that could indicate overspeeding.
[0076] In step 220, the controller 68 resets the endpoint of the joystick 50 or operator input to the maximum speed associated with the selected speed mode of the device 10, in response to the gradient being less than or equal to a predetermined gradient in step 218, or in response to the braking torque being less than a threshold in step 218. This releases the predetermined speed limit from the device 10. In order to limit the calibration hysteresis or cycle of the joystick 50, the controller 68 may require in step 218 that the gradient remain below a predetermined gradient or the braking torque remain below a threshold over time.
[0077] While exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms of the Disclosure. Rather, the language used herein is descriptive, not restrictive, and it should be understood that various modifications can be made without departing from the spirit and scope of the Disclosure. Furthermore, features of various embodiments can be combined to form further embodiments of the Disclosure and the Invention.
Claims
1. A lifting device, Chassis and A lift mechanism that supports the lift platform on the chassis, Multiple traction devices supporting the chassis on the foundation surface, An electric motor driven and connected to at least one of the plurality of traction devices, The electric motor and the traction battery that is electrically connected, A user input unit controls the speed of the lifting device by inputting a requested speed, A controller configured to, in response to the lifting device being on a non-zero gradient and the requested speed being greater than a predetermined speed, to command the electric motor to output braking torque, to supply power to the traction battery, and to limit the speed of the lifting device to the predetermined speed, Equipped with, A lifting device, wherein the controller is further configured to infer that the lifting device is on the non-zero gradient, based on the fact that the output torque of the electric motor is applied in the opposite direction to the rotational speed of the electric motor.
2. In the lift device according to claim 1, The system further includes a parking brake associated with at least one of the aforementioned multiple traction devices, A lifting device in which the controller commands the parking brake to stop the lifting device in response to the braking torque being insufficient to maintain the lifting device at a predetermined speed while on the non-zero gradient.
3. In the lift device according to claim 1, A lifting device, wherein the controller is further configured to output the braking torque and command the electric motor to limit the speed of the lifting device to the predetermined speed when the speed of the lifting device is greater than a threshold.
4. In the lift device according to claim 1, It further includes a hydraulic circuit and a pump motor, The hydraulic circuit includes a pump, a pressure galley, a return line, and a valve. The valve controls the pressure in the pressure galley and fluidly connects the pressure galley to the return line. The pump motor is driven by the pump and electrically connected to the traction battery. A lifting device, wherein the controller is further configured to increase the flow rate of the pump and control the valve to decrease the size of the valve opening in response to the battery parameters being outside a predetermined range while the electric motor is outputting the braking torque and supplying power to the towing battery, thereby increasing the pressure in the pressure galley and reducing the power to the towing battery.
5. In the lift device according to claim 4, A lifting device wherein the hydraulic circuit has an actuator arranged to fluidly connect the pressure galley and the return line, and the actuator is coupled to the lifting mechanism.
6. In the lift device according to claim 1, A lifting device in which the user input unit is equipped with a joystick.
7. In the lift device according to claim 1, A lifting device in which the aforementioned multiple towing devices are not equipped with a service brake system.
8. In the lift device according to claim 1, A lifting device in which the predetermined speed depends on the gradient.
9. In the lift device according to claim 1, A lifting device, wherein the controller is further configured to estimate the gradient as being proportional to the output torque of the electric motor.
10. In the lift device according to claim 1, A lifting device wherein the controller is further configured to estimate the gradient in response to the output torque of the electric motor being greater than a predetermined torque.
11. In the lift device according to claim 1, The chassis further comprises a multi-axis inertial sensor supported by the chassis, The controller is further configured to receive a signal indicating the gradient from the multi-axis inertial sensor, in a lifting device.
12. A lifting device, Chassis and A lift mechanism that supports the lift platform on the chassis, Multiple traction devices supporting the chassis on the foundation surface, An electric motor driven and connected to at least one of the plurality of traction devices, The electric motor and the traction battery that is electrically connected, A user input unit controls the speed of the lifting device by inputting a requested speed, A controller configured to, in response to the lifting device being on a non-zero gradient and the requested speed being greater than a predetermined speed, to command the electric motor to output braking torque, to supply power to the traction battery, and to limit the speed of the lifting device to the predetermined speed, A multi-axis acceleration sensor supported by the chassis is provided, A lifting device, wherein the controller is further configured to receive a signal from the multi-axis acceleration sensor and to estimate the gradient from the signal by either removing an acceleration component determined from a change in the rotational speed of one of the traction devices, or by applying a filter based on the acceleration component to the signal.
13. In the lift device according to claim 12, A lift device in which the filter is modulated based on the acceleration component.
14. In the lift device according to claim 12, A lifting device wherein the filter is an exponential filter, and the time constant of the filter depends on the acceleration component.
15. In the lift device according to claim 12, A lift device in which the filter is a single exponential filter.
16. In the lift device according to claim 1, The controller is further configured to release the speed limit of the lift device in response to the non-zero gradient being less than a predetermined gradient.
17. A method for controlling a lifting device, The user input unit receives the requested speed of the lift device, The lifting device is propelled at the required speed via an electric motor connected to the wheels, wherein the electric motor is electrically connected to a traction battery. The determination that the requested speed is greater than a predetermined speed when the lifting device is on a non-zero gradient, and that the predetermined speed depends on the gradient, While the lift device is on the non-zero gradient, the electric motor is commanded to output braking torque and supply power to the towing battery, thereby limiting the speed of the lift device to the predetermined speed, and while the lift device is on the non-zero gradient, if the speed of the lift device exceeds the predetermined speed, the parking brake is commanded to stop the lift device. A method that includes [a certain feature].