Wired steering system

Abstract

The invention relates to a wired steering system (1) for operating a vehicle with a steering mechanism (8), having a steering input device (2) and a first actuation arrangement (5), the first actuation arrangement (5) comprising a first electric motor (5a) connected to the steering input device (2) and a first hydraulic unit (5d) operably coupled to the first electric motor (5a), the first hydraulic unit (5) is configured to be in fluid connection with the steering mechanism (8). The object of the invention is to provide a wired steering system (1) with a wide range of steering forces. This is achieved by a wired steering system (1) comprising a second actuation arrangement (6) constructed and coupled similar to the first actuation arrangement (5).

Description

Technical Field

[0001] The present invention relates to a wire steering system for steering a vehicle by means of a steering mechanism, the wire steering system having a steering input device and a first actuation arrangement, wherein the first actuation arrangement includes a first electric motor connected to the steering input device and a first hydraulic unit operatively coupled to the first electric motor, and wherein the first hydraulic unit is configured to be fluidly connected to the steering mechanism. Background Art

[0002] The vehicle is, for example, a construction vehicle, an agricultural vehicle, a mining vehicle or a similar vehicle. Even though the preferred embodiments are off-road, the system can also be used on roads, for example, on trucks or buses. Such a vehicle is steered by a steering input device including, for example, a steering wheel and / or a joystick or another input device, or the vehicle steers completely automatically. The steering input device detects the driver's steering input and determines a steering command based on the steering input and provides it to the actuation arrangement. The actuation arrangement including the electric motor and the hydraulic unit receives the steering command and controls the electric motor to drive the hydraulic unit based on the steering command. The hydraulic unit supplies hydraulic fluid to a steering mechanism including at least one hydraulic cylinder to maneuver the vehicle, in particular its steering wheels.

[0003] For example, the electric motor drives the hydraulic unit, where the hydraulic unit is a hydraulic pump or a hydraulic steering unit. In the case where the hydraulic unit is a hydraulic steering unit, the hydraulic fluid is provided by an external pressure source (such as a system pump), such that the electric motor acts as the actuation arrangement. The steering assembly, in particular at least one hydraulic cylinder, is supplied with hydraulic pressure by the hydraulic steering unit. The hydraulic steering unit includes a rotary valve and a rotary meter driven by a common drive shaft driven by the electric motor. In the case where the hydraulic unit is a pump, the electric motor powers and drives the hydraulic pump, and the hydraulic pump generates hydraulic pressure to drive the steering mechanism and its (multiple) hydraulic cylinders. Summary of the Invention

[0004] The object of the present invention is to provide a wire steering system having a wide range of steering forces.

[0005] This object is achieved by the steering system according to claim 1.

[0006] The wired steering system as described at the beginning includes a second actuation arrangement, wherein the second actuation arrangement includes a second electric motor connected to the steering input device and a second hydraulic unit operatively coupled to the second electric motor, and wherein the second hydraulic unit is configured to be fluidly connected to the steering mechanism. Both hydraulic units of the first actuation arrangement and the second actuation arrangement are fluidly connected to each hydraulic cylinder of the steering mechanism. If one actuation arrangement fails, the other actuation arrangement is still able to perform the steering operation, such that this wired steering is fail operational. Thus, the wired steering system is at least partially redundant, allowing for a safe stop in the event of a failure of one actuation arrangement.

[0007] In one embodiment, the wired steering system includes at least one vehicle speed sensor and / or at least one wheel angle sensor. The vehicle speed sensor is configured to provide information about the vehicle speed. The wheel angle sensor is configured to provide information about the angle of at least one steering wheel relative to the normal position, e.g., the position of the wheels when the vehicle is traveling straight forward. By using the information provided by the wheel angle sensor and / or the vehicle speed sensor, the sensitivity of the wired steering system can be adjusted. For example, when the vehicle is traveling slowly, the steering command provided to the steering input device results in a greater steering angle compared to the steering command at a higher vehicle speed. This allows for good user-friendliness.

[0008] In one embodiment, the steering input device includes two steering input sensors, wherein both steering input sensors are data-connected to the first electric motor and the second electric motor. However, more steering input sensors can be provided, wherein all sensors are data-connected to each electric motor. Each sensor is connected to the corresponding controller of the electric motor. By comparing the signals provided by different steering input sensors, the tolerances of each steering input sensor can be taken into account, thus enabling precise steering of the vehicle. By comparing the sensor outputs from the sensors, it can also be determined whether one of the sensors is faulty.

[0009] In one embodiment, the steering input device includes a feedback module. Such a steering feedback module provides tactile and sensory information to the driver through the steering input device, in particular through the handle of the steering input device, e.g., the steering wheel. Thus, the driver or operator senses, for example, when the maximum steering angle is reached and / or when the center position is reached. In a preferred embodiment, the feedback module is in the form of an electric motor, and the same motor also serves as a steering input sensor.

[0010] In one embodiment, the steering input device is fail-operational. To this end, the steering input device includes redundant sensors and / or data connections to other components of the wired steering system, such as a first actuation arrangement and a second actuation arrangement. By providing a fail-operational steering input device to the wired steering system, the wired steering system is operable even if at least one component of the steering input device fails. The fail operation can be in the form of an electric motor having two sets of windings, such that if the first pair of windings fails, the steering input device can still be used.

[0011] In one embodiment, each electric motor is connected to a corresponding controller, where the controller is connected to at least one sensor assembly, in particular at least one vehicle speed sensor, at least one wheel angle sensor, and / or two steering input sensors. Each controller is configured to control the electric motor based on information provided by the at least one sensor assembly. Additionally, information provided by other sensors, such as a steering speed sensor, a rotational speed sensor of the electric motor, etc., can also be used. This allows for precise steering. In a preferred embodiment, the electric motor and at least one controller are integrated in the same housing.

[0012] In one embodiment, at least one of the first actuation arrangement or the second actuation arrangement includes a transmission unit disposed between the corresponding electric motor and the corresponding hydraulic unit. The transmission unit couples the corresponding electric motor to the corresponding hydraulic unit. In another actuation arrangement, for example, the output element of the first electric motor drives the input element of the first hydraulic unit, where the input element of the first hydraulic unit and the output element of the first electric motor interact directly with each other. Alternatively, both actuation arrangements include a transmission unit, where the transmission units differ in their transmission (gear) ratio. The transmission unit reduces or increases the torque provided by the electric motor to the hydraulic pump. By increasing the torque, the speed is reduced and vice versa. Higher torque results in higher steering force and lower steering speed, while higher speed results in faster steering speed and lower steering force.

[0013] In one embodiment, the second actuation arrangement is a backup for the first actuation arrangement. In this embodiment, the second actuation arrangement only operates when the first actuation arrangement fails. This results in low wear of the second actuation arrangement.

[0014] In one embodiment, the first actuation arrangement is configured to operate in a first state, the second actuation arrangement is configured to operate in a second state and / or the first actuation arrangement and the second actuation arrangement are configured to operate together in a third state. For example, the first state is when a very small steering speed is required to steer the vehicle. In the second state, a medium-high steering speed is required, while in the third state a high steering speed is required to steer the vehicle. Or, in other words, the first actuation arrangement and the second actuation arrangement operate alternately, where the first actuation arrangement operates in a first time period and the second actuation arrangement operates in a second time period. In another embodiment, the first actuation arrangement and the second actuation arrangement always operate simultaneously. In another example, the first actuation arrangement operates in a first state, where when the state changes, for example when a higher steering speed is required, the second actuation arrangement supports the first actuation arrangement. For example, the first actuation arrangement and the second actuation arrangement are different from each other, where the electric motor of the second actuation arrangement provides a higher torque than the electric motor of the first actuation arrangement. Or, the first actuation arrangement and the second actuation arrangement are the same. This enables the steer-by-wire system to highly flexibly adapt to different types of vehicles. When both actuation arrangements are actuated simultaneously, this ensures that nothing is sucked in, as the mechanical system is activated each time. In this way, the two columns can provide 50% of the total amount of fluid required for steering.

[0015] In one embodiment, the GPS unit is data-connected to the first actuation arrangement and the second actuation arrangement. Preferably, the GPS unit is data-connected to the controllers of the electric motors of each actuation arrangement. This allows the vehicle to steer fully automatically based on the information provided by the GPS unit. Since the GPS signal is received on both actuation units, redundant signals can also be ensured if one of the units fails. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be described below with reference to the preferred embodiments in conjunction with the accompanying drawings. Schematically shown herein are:

[0017] Figure 1 : A first embodiment of the steer-by-wire system;

[0018] Figure 2 : A second embodiment of the steer-by-wire system; and

[0019] Figure 3 : A third embodiment of the steer-by-wire system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] Hereinafter, the same and similar elements share the same reference numerals.

[0021] Figure 1Illustrates a first embodiment of a steer-by-wire system 1, which has a steering input device 2 with a steering wheel 3. The steering input device 2 is in a data connection 4 with a first actuation arrangement 5 and a second actuation arrangement 6. The two actuation arrangements 5, 6 are fluidly connected via a hydraulic line 7 to a hydraulic cylinder 8 of a steering mechanism (not further shown).

[0022] The steering input device 2 includes a steering input sensor 9 (see Figure 2 , Figure 1 and Figure 3 not shown in), which can be, for example, a torque sensor and / or a position sensor. The steering input device 2 may include a feedback module 10, see Figure 2 . The steering input device 2 is first connected to a power supply (not shown) via an input power supply 11. The steering input device may also include a gear arranged, for example, between the steering wheel and an electric motor. The electric motor may be connected to the steering unit by a spline connection, which is generally the way the steering wheel is connected to a hydraulic steering unit, and it may also be a special connection designed to minimize the gap between the two units. The electric motor and the controller may also be integrated with the steering unit in the same housing.

[0023] The first actuation arrangement 5 includes a first electric motor 5a, a first power supply 5b, a first controller 5c, and a first hydraulic unit 5d. The first controller 5c is in a data connection with the steering input device 2. The first hydraulic unit 5d is connected to the hydraulic cylinder 8 via the hydraulic line 7. Similar to the first actuation arrangement 5, the second actuation arrangement 6 includes a second electric motor 6a, a second power supply (not shown), a second controller 6c, and a hydraulic unit 6d. The second controller 6c is in a data connection with the steering input device 2. The second hydraulic unit 6d is connected to the hydraulic cylinder 8 via the hydraulic line 7. The steering input sensor 9 is in a data connection with the first electric motor 5a and the second electric motor 6a and their controllers 5c, 6c, respectively. In addition, the second actuation arrangement 6 is constructed in the same way as the first actuation arrangement 5. The two controllers 5c and 6c may also be connected to each other so that they can exchange information, for example, by comparing the information received from the sensors in the steering input device, which can be used to indicate a faulty sensor in the steering input device.

[0024] The hydraulic unit receives fluid from a pump (not shown) and returns the fluid to a fuel tank (also not shown).

[0025] Figure 2Illustrates a second embodiment of a wire steering system 1, which has all the features of the first embodiment. The wire steering system 1 includes a steering input device 2 having a steering wheel 3, two steering input sensors 9, a feedback module 10, and is connected to a power source through an input power supply 11. The steering input device 2, in particular the steering input sensors 9, is connected to each of the first electric motor 5a and the second electric motor 6a through a data connection 4, a corresponding wire 4, in particular to their controllers 5c, 6c. The first actuation arrangement 5 includes a first electric motor 5a, a first power supply 5b, a first controller 5c, and a first hydraulic unit 5d. The second actuation arrangement 6 includes a second electric motor 6a, a second power supply (not shown), and a second hydraulic unit 6d. The two hydraulic units 5d, 6d are fluidly connected to a steering mechanism through a hydraulic line 7, which particularly includes a hydraulic cylinder 8. In addition, the second embodiment includes a GPS unit 12 that is data-connected to a GPS controller 13 and to the first controller 5c and the second controller 6c.

[0026] Figure 3 Illustrates a third embodiment of a wire steering system 1 similar to the first embodiment. The wire steering system 1 includes a steering input device 2 having a steering wheel 3. Power is supplied to the steering input device 2 via an input power supply 11. The steering input device 2 includes a feedback module and steering input sensors (not shown). In addition, the steering input device 2 is data-connected to the first actuation arrangement 5 and the second actuation arrangement 6, in particular to their controllers 5c, 6c. Each of the steering input sensors 9 is respectively connected to each of the electric motors 5a, 6a and their controllers 5c, 6c. The first actuation arrangement 5 includes an electric motor 5a, a first power supply 5b, a first controller 5c, and a first hydraulic unit 5d. The second actuation arrangement 6 includes a second electric motor 6a, a second power supply (not shown), and a second hydraulic unit 6d. The first hydraulic unit 5d and the second hydraulic unit 6d are fluidly connected to a hydraulic cylinder 8 of a steering mechanism via a hydraulic line 7. In addition, the second actuation arrangement 6 includes a transmission unit 6e disposed between the second electric motor 6a and the second hydraulic unit 6d. The transmission unit 6e can be used to increase or decrease the torque generated by the second electric motor 6a before supplying it to the second hydraulic unit 6d.

[0027] According to the design of the transmission unit 6e, the speed or torque provided by the second electric motor 5a increases while the corresponding other one decreases. As a result, high torque or high speed is provided to the second hydraulic unit 6c, and the second hydraulic unit 6c provides a corresponding high pressure or high flow rate to the hydraulic cylinder 8.

[0028] The first embodiment, the second embodiment, and the third embodiment can be combined to form an unillustrated fourth embodiment of the wire steering system 1 having a GPS unit 12 and a transmission unit 6e.

[0029] In all embodiments, the first electric motor 5a is controlled via a first controller 5c. The first electric motor 5a is operatively coupled to a first hydraulic unit 5d. Thus, the first electric motor 5a drives the first hydraulic unit 5d. The first hydraulic unit 5d is fluidly connected to the hydraulic cylinder 8.

[0030] The above-described wired steering system 1 can be used, for example, in vehicles, particularly mining vehicles, agricultural vehicles, construction vehicles, heavy forklifts, etc.

[0031] In addition to the above features, the wired steering system 1 further includes at least one vehicle speed sensor and / or at least one wheel angle sensor. The at least one vehicle speed sensor is configured to provide information on the vehicle speed. The at least one wheel angle sensor provides information on the angle of the steering wheel relative to a neutral position (e.g., the position where the vehicle moves in a straight line). Depending on the design of the vehicle, multiple steering wheels or the like, wheel angle sensors can be provided on each steering wheel. The at least one vehicle speed sensor, the at least one wheel angle sensor, and / or two steering input sensors (9) form a sensor assembly (not shown). This sensor assembly maintains a data connection with both the first controller 5c and the second controller 6c.

[0032] During operation, the operator provides a steering input to the steering input device 2 via the steering wheel 3 or a joystick (not shown). The steering input sensor 9 detects the movement of the steering wheel 3 and provides corresponding information on the movement to the first controller 5c and the second controller 6c. Based on the information provided by the steering input sensor 9, and the sensor assembly including the vehicle speed sensor, the status and / or the wheel angle sensor, each of the controllers 5c, 6c controls its respective electric motor 5a, 6a to operate the correspondingly coupled hydraulic units 5d, 6d, so as to provide an appropriate hydraulic flow rate to the hydraulic cylinder 8.

[0033] Alternatively, the vehicle can be controlled by a satellite navigation system unit (e.g., GPS unit 12). The GPS unit 12 is configured to use the Global Positioning System GPS to automatically steer the vehicle based on the vehicle's position. For this purpose, the GPS unit 12, the GPS controller 13 respectively provide information to each of the controllers 5c, 6c of the actuation arrangements 5, 6, such that the actuation arrangements 5, 6 provide a hydraulic flow to actuate the hydraulic cylinder 8. In addition, a satellite navigation system can also be employed.

[0034] In the first state, only the first actuation arrangement 5 operates the steering mechanism to steer the vehicle. In the second state, only the second actuation arrangement 6 operates the steering mechanism to steer the vehicle. In the third state, both the first actuation arrangement 5 and the second actuation arrangement 6 operate the steering mechanism of the vehicle.

[0035] The state used depends on, for example, the force required to turn the steering wheel to provide a change in the wheel angle. For example, in a stationary state, a high steering force is required, while in a moving state of the vehicle, the steering force is lower. In any state, one of the two actuation arrangements 5, 6 can provide sufficient steering to safely park the vehicle in the event of a failure of one of the actuation arrangements 5, 6.

[0036] In the first and second states, the respective other actuation arrangements 5, 6 are configured as backup devices for operating the actuation arrangements 5, 6 in the event of a failure of the operating actuation arrangements 6, 5.

[0037] In the third state, the first actuation arrangement 5 and the second actuation arrangement 6 work together to provide a hydraulic output to the hydraulic cylinder 8. This allows for a high steering force or a high flow rate. In addition, since both actuation arrangements 5, 6 generate the required force, the load on a single actuation arrangement 5, 6 is lower.

[0038] A system pump (not shown) supplies / pumps pressurized fluid from a reservoir (not shown) to the actuation arrangements 5, 6, in particular to the respective hydraulic units 5d, 6d.

[0039] The functions of the actuation arrangements 5, 6 are described below. Each of the hydraulic units 5d, 6d includes a rotary valve (not described) and a rotary meter driven by a common drive shaft driven by the respective electric motors 5a, 6a. The rotary valve determines, based on the rotation of the drive shaft, into which of the hydraulic lines 7 the pressurized (steering) fluid should be directed and thus whether the steering cylinder 8 provides movement of the wheels to the left or to the right. The rotary valve simultaneously opens a passage in another hydraulic line 7 between the actuation arrangements 5, 6 and the reservoir to return the (steering) fluid to the reservoir.

[0040] Each actuation arrangement 5, 6 can include a pressure relief valve (not shown) and an anti-cavitation valve (not shown). The system pump and the optional actuation arrangements 5, 6 can be combined into a single power pack accommodated in a single housing. In fact, the entire actuation arrangement 5, 6 can be combined into a single unit formed by a housing that houses all the components of the actuation arrangements 5, 6 and optionally also a reservoir for the steering fluid.

[0041] During normal operation, the steering signal provided by the steering input device 2 indicates a relatively small rotation of the rotary valve and the rotary instrument. This signal can be generated, for example, based on the movement of a joystick or a steering wheel 3 that operates an electrical sensor of the steering input device 2. In a fault operation, the electric motors 5a, 6a, and in particular the corresponding controllers 5c, 6c, receive a signal indicating a relatively large rotation of the rotary valve and the rotary instrument to operate the rotary instrument as pumps 5d, 6d. To indicate the transition between the two operating modes, each actuation arrangement 5, 6 can include a sensor, such as a pressure sensor, adapted to indicate a system pump failure.

[0042] Additionally or alternatively, the wire steering system 1 includes at least one directional valve (not shown) and at least one metering pump unit (not shown), each metering pump unit having two metering pumps 5d, 6d. The metering pumps 5d, 6d can be hydraulically connected in parallel, with a shut-off valve (not shown) arranged between the metering pumps 5d and 6d. The two metering pumps 5d, 6d are connected to a common (not shown) steering shaft, which can be actuated by the electric motors 5a, 6a. The metering pumps 5d, 6d are fluidly connected to the steering cylinders 8.

[0043] When the steering shaft rotates, the directional valve opens a path from the pump connection (connecting the system pump to the actuation arrangements 5, 6) to one of the two hydraulic lines 7, and another path from the hydraulic line 7 to the reservoir. In most cases, the directional valve includes a valve element in the form of two concentric cylinders, commonly referred to as a spool and a sleeve. The rotation of the steering shaft causes a rotation between the shaft and the spool. When the hydraulic fluid (steering fluid) passes through the metering pumps 5d, 6d, the metering pumps 5d, 6d are driven to rotate the spool and the sleeve back to their neutral positions.

[0044] During normal operation, the metering pumps are in an operating state, and the total displacement is the sum of the metering pumps 5d, 6d. In the case of a failure of one of the metering pumps 5d, 6d, the shut-off valve will switch so that only the steering fluid from one metering pump 5d, 6d (remaining active) is directed to the steering cylinder 8, enabling the corresponding electric motor 5a, 6a to build up the required steering pressure due to the minimum displacement of the entire steering unit. In this case, the chambers of the remaining metering pump 5d, 6d are all connected to each other through the shut-off valve, so that no flow and pressure are generated from this metering pump 5d, 6d.

[0045] In the case where the wire steering system 1 includes two steering cylinders 8, where each steering cylinder 8 is connected to one of the actuation arrangements 5, 6, each actuation arrangement 5, 6 includes a reaction valve or a bypass valve to allow fluid flow even if one of the actuation arrangements 5, 6 fails. The reaction valve or the bypass valve is integrated in the spool / sleeve assembly, where the spool / sleeve assembly is formed by the sleeve and the spool. This allows for connection through the steering unit / measurement motor in the neutral position.

[0046] For example, the actuation arrangements 5, 6 are OSP units of Danfoss.

[0047] In a variant, the steering mechanism provides two hydraulic cylinders, such as a first steering cylinder and a second steering cylinder. Both the first hydraulic unit 5d and the second hydraulic unit 6c can be hydraulically connected to the two steering cylinders. If the two steering cylinders are configured to steer the same wheel(s), it may be sufficient to hydraulically connect the first hydraulic unit 5d to the first hydraulic cylinder and the second hydraulic unit 6d to the second steering cylinder. Even if one of the steering cylinders or hydraulic units 5d, 6d fails, the system remains operational so that the vehicle can be safely parked.

Claims

1. A wire steering system (1) for maneuvering a vehicle using a steering mechanism (8), the wire steering system (1) having a steering input device (2) and a first actuation arrangement (5), wherein the first actuation arrangement (5) comprises: A first electric motor (5a) connected to the steering input device (2); and a first hydraulic unit (5d) operatively coupled to the first electric motor (5a), wherein the first hydraulic unit (5d) is configured to be in fluid connection with the steering mechanism (8). The wired steering system (1) is characterized in that it includes a second actuation arrangement (6), wherein the second actuation arrangement (6) includes: a second electric motor (6a) connected to the steering input device (2); and a second hydraulic unit (6d) operatively coupled to the second electric motor (6a), wherein the second hydraulic unit (6d) is configured to be in fluid connection with the steering mechanism (8).

2. The wired steering system (1) according to claim 1, wherein the wired steering system (1) includes at least one vehicle speed sensor and / or at least one wheel angle sensor.

3. The wired steering system (1) according to claim 1 or 2, wherein the steering input device (2) includes two steering input sensors (9), and both of the two steering input sensors (9) are in data connection with the first electric motor (5a) and the second electric motor (6a).

4. The wired steering system (1) according to any one of claims 1 to 3, wherein the steering input device (2) includes a feedback module (10).

5. The wired steering system (1) according to any one of claims 1 to 4, wherein the steering input device (2) is fail-operational.

6. The wired steering system (1) according to any one of claims 1 to 5, wherein each electric motor (5a, 6a) is connected to a corresponding controller (5c, 6c), and the controller (5c, 6c) is connected to at least one sensor assembly, in particular to at least one vehicle speed sensor, at least one wheel angle sensor and / or two steering input sensors (9).

7. The wired steering system (1) according to any one of claims 1 to 6, wherein at least one of the first actuation arrangement (5) or the second actuation arrangement (6) includes a transmission unit (6e) arranged between the respective electric motor (6a) and the corresponding hydraulic unit (6d).

8. The wired steering system (1) according to any one of claims 1 to 7, wherein the second actuation arrangement (6) is a backup device for the first actuation arrangement (5).

9. The wired steering system (1) according to any one of claims 1 to 7, wherein the first actuation arrangement (5) is configured to operate in a first state, the second actuation arrangement (6) is configured to operate in a second state, and / or the first actuation arrangement (5) and the second actuation arrangement (6) are configured to operate together in a third state.

10. The wired steering system (1) according to any one of claims 1 to 9, wherein, A satellite navigation system unit (12) is in data connection with the first actuation arrangement (5) and the second actuation arrangement (6).

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