Description:HAPTIC SYSTEM FOR ‘STEER BY WIRE’ MECHANISM OF MULTI AXLE VEHICLES
Field of the invention:
The present invention generally relates to a haptic system for vehicle and more particularly it relates to a haptic system for “steer by wire” mechanism of hydraulically controlled, heavy duty, multi axle construction vehicle.
Background of the invention:
Conventional steering systems are provided with a mechanical linkage connecting the steering handle to the steering actuator. In the conventional steering mechanism, the operator experiences the steering feedback on the steering handle which is result of moments and the forces acting on the tires (steering actuator). Heavy duty, multi axle construction vehicles, generally referred as “steer-by-wire” vehicles require the input of steering commands through a steering handle to accomplish directional control, as in the multi axle off-highway construction equipment, the axles are indirectly controlled by the controller which breaks the natural torque feedback to the operator. There is no actual mechanical link between axles & the steering handle. This leads to loss of critical data to operator, leading to disorientation of the operator during turnings. A phase lag may occur when the operator applies a fast steering input at the steering handle but the directional control actuator has difficulty keeping in correspondence with the operator's steering command. Haptic mechanism is often used to deal with the problem. Current technologies of haptic steering are: variable load actuator using an electromagnetic clutch / brake; magneto rheological fluid based tactile feedback device; DC motors working in torque control mode; hydraulic torque motor with bypass valve, etc. However, the direction based torque application is not possible in existing electromagnetic clutch / hydraulic torque motor system. The existing system gets deactivated after power off, making the steering handle free. Further, the current systems need specific control mechanisms and can’t utilize standard power steering units.
Accordingly, there exists a need to provide a haptic system for “steer by wire” steering system that can overcome the drawbacks in the prior art.
Objects of the invention:
An object of the present invention is to provide haptic feeling in counterclockwise and clockwise direction to a ‘steer by wire’ steering system of multi axle vehicles.
Another object of the present invention is to block the movement of steering handle during power OFF condition.
Still another object of the present invention is to utilize standard hydraulic power steering unit to provide haptic system for “steer by wire” steering system of multi axle vehicles.
Yet another object of the present invention is to minimize the number of components for construction of a haptic system for “steer by wire” system of multi axle vehicles.
Summary of the invention
In one aspect, the present invention provides a haptic system for steer-by-wire mechanism of multi-axle vehicles. The multi-axle vehicles have a steering handle with a first rotary encoder disposed thereon for sensing a steering handle angle and producing a signal indicative of the steering handle angle. An axle unit includes a plurality of axles with a second rotary encoder disposed on each axle for sensing an angle of rotation thereof and producing a signal indicative of the angle of rotation of the axle. A controller is in operable communication with the first rotary encoder and the second rotary encoder, wherein the controller generates the target angle of rotation for all axles based on a selected steering mode. The haptic system comprises an axle direction control valve, a hydraulic cylinder, a steering pump, a steering tightening module, a first haptic control valve and a second haptic control valve. The axle direction control valve is operably connected to the controller. The hydraulic cylinder is fitted on the axle and is controlled by the axle direction control valve to rotate & achieve the target angle of rotation of the axle with its push pull action. The steering pump provided with a right port and a left port receives the hydraulic oil from a fluid tank through a line P. The hydraulic oil flows back to the fluid tank either through the right port or the left port on rotation of the steering handle respectively in clockwise and counterclockwise direction. The steering tightening module is in signal communication with the controller for receiving the signal indicative of the steering handle angle and the signal indicative of the angle of rotation of the axle there from. The steering tightening module generates the signal indicative of a desired steering handle feedback torque. The first haptic control valve and the second haptic control valve are in signal communication with the steering tightening module and fluidically connected respectively to the right port and the left port for controlling the flow of hydraulic fluid there from to provide the desired steering handle feedback torque on rotation of steering handle in clockwise direction and counterclockwise direction.
In another aspect, the resent invention provides a method for providing haptic feedback in a steer by-wire system of multi-axle vehicle. In first step, the method comprises powering ON an engine of the multi-axle vehicle and selecting a steering mode. In next step, the method comprises generating a target value of angle of rotation for each axle based on the steering mode and communicating the target value of angle of rotation to an axle direction control valve fitted on the axle. In next step, the method comprises receiving a signal indicative of the steering handle angle from a first rotary encoder disposed relative to a steering handle. In next step, the method comprises receiving a signal indicative of the angle of rotation of the axle from a second rotary encoder disposed relative to each axle. In next step, the method comprises generating a signal indicative of a desired steering handle feedback torque by processing the signals from the first rotary encoder and the second rotary encoder in a steering tightening module and controlling a flow of hydraulic fluid from a right port and a left port of a steering pump by operating a first haptic control valve and a second haptic control valve by the steering tightening module thereby generating a steering handle feedback torque in clockwise and counterclockwise direction.
Brief description of the drawings:
The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein
Figure 1, 2, 3 and 4 respectively show axle positions in front wheel steering mode, rear wheel steering mode, all wheel steering mode and crab steering mode, for a multi-axle vehicle;
Figure 5 shows a flow chart of stages of closed loop control of steering axles in a steer-by-wire mechanism in accordance with the present invention;
Figure 6 shows flow chart of stages of control of haptic steering valves in a steer-by-wire mechanism in accordance with the present invention;
Figure 7 shows the haptic system for ‘steer by wire’ mechanism of multi axle vehicles, in accordance with the present invention, wherein blue lines indicate hydraulic connections and red lines indicate electrical connections;
Figure 8 shows control mechanism of haptic system for ‘steer by wire’ mechanism of multi axle vehicles, in accordance with the present invention;
Figure 9 shows hydraulic circuit of haptic system for ‘steer by wire’ mechanism of multi axle vehicles, in accordance with the present invention; and
Figure 10 shows graph of steering error vs percentage of maximum torque generated on steering handle, in accordance with the present invention.
Detailed description of the embodiments:
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiments.
The present invention provides a system for providing haptic feedback for a steering of multi axle vehicles. Referring to figures 1 to 4, the multi-axle vehicles operate on multiple steering modes e.g. front wheel steering mode (fig. 1, automotive steering), rear wheel steering mode (fig 2, forklift steering), all wheel steering mode (fig.3, hybrid of both automotive & forklift), crab steering mode (fig.4, all axles position parallel to each other), etc. Since one steering pump can’t control multiple axles (as their target angle values change from mode to mode) or multiple steering pumps can’t be provided for all axles, a first rotary encoder is provided below a steering column of the vehicle, that receives the desired steering angle from the operator. A controller in operable communication with the first rotary encoder communicates the information of desired steering angle and the steering mode to a second rotary encoder fitted on each axle of the vehicle. A hydraulic cylinder fitted on each axle and controlled by a proportional control valve with a push pull action powers the axle to rotate & achieve the target angles. The controller continuously monitors the actual steering handle angle and generates the target value of all axles based on the steering mode. On evaluating the actual angle data coming from the encoders mounted on each axles & the target values, the controller generates signals to haptic control valves. The error which is the difference between the target and the actual values is processed by the controller to calculate the haptic control valve signals which in turn generates tightening of steering handle in each direction of rotation.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description and in the table below.
Table:
Ref No: Component Ref No: Component
10 Steering handle 40 Main pump
12 Steering column, 45 Fluid tank
15 First rotary encoder (steering) 50 Controller
20 Steering pump 60 Axle unit
22 Right port of steering pump 65 Axles
24 Left port of steering pump 62 Second rotary encoder (axle)
30 First haptic control valve 64 Axle direction control valve
32 Second haptic control valve 66 Hydraulic cylinder
34 Steering tightening module 120 Engine
Referring to the figures 5 to 8, a haptic system (100) for ‘steer by wire’ mechanism of multi axle vehicles (herein after referred to as “the system (100)”) in accordance with the present invention is shown. The system (100) comprises of a steering unit, an axle unit (60) and a haptic control unit in operable communication with each other through a controller (50).
The multi-axle steer-by-wire mechanism of the multi-axle vehicle includes a steering unit, an axle unit (60) and a controller (50). The steering unit includes a steering handle (10) fitted on a steering column (12). A first rotary encoder (15) is disposed on the steering column (12) relative to the steering handle (10) for sensing a steering handle angle and for producing a signal indicative of the steering handle angle. A controller (50) is operably connected to the first rotary encoder (15) for continuously monitoring the steering handle angle. A steering mode is selected using the selector keys provided on user interface in operator’s cabin. The user interface is in signal communication with the controller (50).
The axle unit (60) includes a plurality of axles (65) with a second rotary encoder (62) disposed relative to each axle (65) for sensing an angle of rotation thereof and producing a signal indicative of the angle of rotation of the axle (65). The axle unit (60) is in operable communication with the steering unit through the controller (50). Based on the steering mode, the controller (50) generates the target value of angle of rotation for all axles (65).
The system (100) comprises an axle direction control valve (64), a hydraulic cylinder (66), a steering pump (20), a first haptic control valve (30), a second haptic control valve (32), a steering tightening module (34), a main pump (40), and a fluid tank (45).
The axle direction control valve (64) is fitted on each axle (65) and is operably connected to the controller (50). The hydraulic cylinder (66) fitted on the axle (65) is controlled by the axle direction control valve (64). On receiving the target value of angle of rotation for all axles (65), the axle direction control valve (64) operates and controls the hydraulic cylinder (66) for powering the axle (60) to rotate & achieve the target angle of rotation with push pull action.
The steering pump (20) provided with a right port (22) and a left port (24), is fluidically connected through a line ‘P’ to the main pump (40). The main pump (40) is driven by an engine (120). The main pump (40) supplies hydraulic oil from the fluid tank (45) to the steering pump (20) through the line ‘P’. On rotation of the steering handle (10), the hydraulic fluid flows back to the fluid tank through the right port (22) and the left port (24). The flow of hydraulic oil back to the fluid tank (45) through the right port (22) and the left port (24) is controlled by the first haptic control valve (30) and the second haptic control valve (32). In an embodiment, the hydraulic oil flows out through the right port (22) on rotation of the steering handle (10) in clockwise (CW) direction and the hydraulic oil flows out through the left port (24) on rotation of the steering handle (10) in counterclockwise (CCW) direction. The steering handle (20) becomes tight to rotate when the corresponding port (22/ 24) is blocked. This phenomenon is used in this invention to simulate variable heavy feeling to operator based on the errors in multiple axles.
The steering tightening module (34) is in signal communication with the controller (50) for receiving the signal indicative of the steering handle angle and the signal indicative of the angle of rotation of the axle (65) there from, the steering tightening module (34) generates the signal indicative of a desired steering handle feedback torque. The first haptic control valve (30) and the second haptic control valve (32) are driven by the steering tightening module (34) for controlling the flow of hydraulic fluid from the right port (22) and the left port (24) thereby generating torque for rotation of steering handle (10) in clockwise and counterclockwise direction.
During operation of the system (100), the operator powers ON the engine (120) and selects the steering mode and travel mode. The controller (50) generates the target value of angle of rotation for all axles (65) based on the steering mode. The controller (50) is in communication with the first rotary encoder (15) for receiving the signal indicative of the steering handle angle and with the second rotary encoder (62) for receiving the signal indicative of the actual axle direction. Based on the actual data of the steering handle angle and the axle direction received from the first and the second rotary encoders (15 and 62), the error which is the difference between the target value and the actual value of the steering angle is processed by the steering tightening module (34) to calculate the signal to the first haptic control valve (30) and a second haptic control valve (32) which in turn generates tightening of steering handle in each direction of rotation. Thus, the torque is generated in CW and CCW direction corresponding to the signal indicative of a desired steering handle feedback torque. If all the axles (65) have achieved the target values within required positioning window, both the right port (22) and the left port (24) are fully opened by operating the first haptic control valve (30) and the second haptic control valve (32) to open the right port (22) and the left port (24).
If the steering handle (10) is turned faster in say CW direction than achievable speed of the system (100), the first haptic control valve (30) is operated proportionally to close the corresponding right port (22) as per the error. This gives heavy to steer feeling to the operator.
When the system (100) is not ON and not in a travel mode, the steering handle (10) is blocked for rotation due to no power to the haptic control valves (30, 32) and the axle direction control valve (64). This ensures safety of operation by avoiding accidental steering of axles after starting the travel mode. The steering force for CW & CCW directions can be adjusted at different levels, so that if the errors are too high on one side, the steering handle can be brought back in reverse direction.
Advantages of the invention:
When the system (100) is not ON and not in a travel mode, the steering handle (10) is blocked for rotation due to no power to the haptic control valves (30, 32) and the axle direction control valve (64). This ensures safety by operation by avoiding accidental steering of axles after starting the travel mode.
The steering force for CW & CCW directions can be adjusted at different levels, so that if the errors are too high on one side, the steering handle can be brought back in reverse direction.
The system (100) uses standard hydraulic power steering units & hydraulic parts.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the scope of the claims of the present invention.

, Claims:We claim:
1. A haptic system (100) for steer-by-wire mechanism of multi-axle vehicles having a steering handle (10) with a first rotary encoder (15) disposed thereon for sensing a steering handle angle and producing a signal indicative of the steering handle angle; an axle unit (60) having a plurality of axles (65) with a second rotary encoder (62) disposed on each axle (60) for sensing an angle of rotation thereof and producing a signal indicative of the angle of rotation of the axle (65) and a controller (50) in operable communication with the first rotary encoder (15) and the second rotary encoder (62), wherein the controller (50) generates the target angle of rotation for all axles (65) based on a steering mode; the haptic system (100) comprising:
an axle direction control valve (64) operably connected to the controller (50);
a hydraulic cylinder (66) fitted on the axle (65) and controlled by the axle direction control valve (64) to rotate & achieve the target angle of rotation of the axle (65) with push pull action;
a steering pump (20) provided with a right port (22) and a left port (24), the steering pump (20) receiving hydraulic oil from a fluid tank (45) through a main pump (40), wherein the hydraulic oil flows back to the fluid tank (45) either through the right port (22) or the left port (24) on rotation of the steering handle (10) in clockwise and counterclockwise directions;
a steering tightening module (34) in signal communication with the controller (50) for receiving the signal indicative of the steering handle angle and the signal indicative of the angle of rotation of the axle (65) there from, the steering tightening module (34) generating the signal indicative of a desired steering handle feedback torque;
a first haptic control valve (30) and a second haptic control valve (32) in signal communication with the steering tightening module (34) and fluidically connected respectively to the right port (22) and the left port (24) for controlling the flow of hydraulic fluid there from to provide the desired steering handle feedback torque on rotation of steering handle (10) in clockwise direction and counterclockwise direction.
2. The haptic system (100) as claimed in claim 1, wherein the hydraulic oil flows out through the right port (22) on rotation of the steering handle (10) in clockwise (CW) direction and the hydraulic oil flows out through the left port (24) on rotation of the steering handle (10) in counterclockwise (CCW) direction.
3. The haptic system (100) as claimed in claim 1, wherein the main pump (40) is driven by an engine (120) of the multi-axle vehicle.
4. A method for providing haptic feedback in a steer by-wire system of multi-axle vehicle, the method comprising:
powering ON an engine (120) of the multi-axle vehicle and selecting a steering mode;
generating a target value of angle of rotation for each axle (65) based on the steering mode and communicating the target value of angle of rotation to an axle direction control valve (64) fitted on the axle (65);
receiving a signal indicative of the steering handle angle from a first rotary encoder (15) disposed relative to a steering handle (10);
receiving a signal indicative of the angle of rotation of the axle (65) from a second rotary encoder (62) disposed relative to each axle;
generating a signal indicative of a desired steering handle feedback torque by processing the signals from the first rotary encoder (15) and the second rotary encoder (62) in a steering tightening module (34);
controlling a flow of hydraulic fluid from a right port (22) and a left port (24) of a steering pump (20) by operating a first haptic control valve (30) and a second haptic control valve (32) by the steering tightening module (34) thereby generating steering handle feedback torque in clockwise and counterclockwise direction.
5. The method as claimed in claim 1, wherein the hydraulic oil flows out through the right port (22) on rotation of the steering handle (10) in clockwise (CW) direction and the hydraulic oil flows out through the left port (24) on rotation of the steering handle (10) in counterclockwise (CCW) direction.
Dated this on 30th day of August, 2022

Ashwini Jagdish Kelkar
(Agent for the applicant)
(IN/PA-2461)