Steering-by-wire steering wheel force sensing redundancy device and control strategy

Abstract

The invention is suitable for the field of vehicle steer-by-wire, provides a steer-by-wire steering wheel force sensing redundancy device and a control strategy, and realizes reliable force feedback of a steering wheel through double force sensing redundancy design of a mechanical spring and a road sensing motor. The algorithm comprises the steps of monitoring the state of a road sensing motor in real time, automatically switching to a mechanical redundancy mode when communication loss, current overload and other abnormalities occur, and dynamically adjusting a four-wheel steering strategy according to the vehicle speed, wherein the flexibility is improved through low-speed out-phase steering, and the stability is improved through high-speed in-phase steering. A steering protection mechanism is arranged, and a front wheel fixed transmission ratio and steering angle limitation are triggered after overrun. Through combination of structural redundancy and intelligent control, the reliability and safety of the steer-by-wire system are remarkably improved, and the steer-by-wire system has good control performance and driving experience.

Description

Technical Field

[0001] The present invention belongs to the field of vehicle steer-by-wire, and in particular relates to a steering wheel force sensing redundancy device and a control strategy for steer-by-wire. Background Art

[0002] The development trend of intelligent and electrified vehicles has promoted the development of wire-controlled vehicle chassis. As one of the important technologies of wire-controlled chassis, wire-controlled steering ensures that the vehicle can achieve the same or similar force feedback effect as non-wire-controlled steering vehicles while realizing the steering function. The reliability of the wire-controlled steering system is one of the important indicators of the functional safety of the wire-controlled chassis.

[0003] The steering wheel force feedback of the current wire-controlled steer mainly realizes road feel simulation through the road sense motor under the control of the algorithm. When the road sense motor fails or the mechanical connection between the steering wheel and the road sense motor becomes stuck, the driver will not be able to quickly perceive the steering state of the vehicle through the steering wheel and will not be able to adjust the vehicle's driving trajectory through the steering wheel. Summary of the invention

[0004] The object of the present invention is to provide a steering wheel force sense redundancy device and a control strategy for wire-controlled steering, aiming to solve the technical problems existing in the prior art identified in the background technology.

[0005] The present invention is implemented as follows: a steering wheel force sense redundancy device for wire-controlled steering includes a steering wheel and a steering column, wherein the steering wheel and the steering column are fixed by bolts to form a rotation transmission structure, and the device also includes:

[0006] The steering column is provided with a shaft shoulder positioning, a circlip groove, a hexagonal shaft, a thread line and an A-type keyway, which are respectively used to install an encoder, a deep groove ball bearing, a rotary damper, a spiral spring, a deep groove ball bearing, an A-type flat key and an electromagnetic clutch;

[0007] A fixing frame is also fixedly arranged on the frame, and the fixing frame is used to provide support for the encoder, the rotary damper, the deep groove ball bearing and the spiral spring;

[0008] The rotary damper is connected to the steering column through a hexagonal hole to provide basic damping, and the steering column is driven by an A-type flat key and an electromagnetic clutch;

[0009] The coil spring is connected to the fixing frame through a spring connecting ring to provide redundant mechanical road feel;

[0010] The deep groove ball bearing is used to provide rotational support for the steering column and the fixed frame;

[0011] The end of the steering column is driven by a flat key of type A with the electromagnetic clutch, and the output end of the reducer is driven by a flat key of type A with the electromagnetic clutch. When the electromagnetic clutch is energized, the steering column and the output shaft of the reducer are driven.

[0012] When the road feel motor fails, the electromagnetic clutch is controlled by the vehicle controller to disconnect, so that the steering column is disengaged from the reducer.

[0013] Another object of the present invention is to provide a redundant control strategy for the steering wheel force feeling of steer-by-wire, which is used to control the redundant device for the steering wheel force feeling of steer-by-wire. The redundant control strategy for the steering wheel force feeling of steer-by-wire includes:

[0014] Step 1: The steering wheel angle θ and the steering speed signal are collected in real time by the encoder and transmitted to the vehicle controller. The vehicle controller distributes the steering wheel angle according to the vehicle speed and the steering speed signal.

[0015] Step 2: The vehicle controller monitors the bus current, torque and encoder position of the road feel motor, sets the monitoring standard. If the monitoring result of the vehicle controller exceeds the monitoring standard, the electromagnetic clutch is controlled to disconnect.

[0016] Step 3: When the electromagnetic clutch is energized, the road feel motor and the helical spring jointly provide superimposed damping, rotational stiffness and rotational torque, and select the steering mode according to the vehicle speed.

[0017] Step 4: When the electromagnetic clutch is de-energized, the mechanical road feel is provided by the redundant device for the steering wheel force feeling. Four-wheel steering is closed, the rear wheels return to zero, and the front wheels perform Ackerman steering with a fixed transmission ratio.

[0018] If the steering wheel angle exceeds ±90°, the protection mechanism is triggered.

[0019] Among them, for the mechanical road feel, the additional torque T provided by the helical spring is calculated according to the steering wheel angle θ ′ , and is superimposed with the initial torque T 0 to obtain the total torque, where:

[0020] T′ = 4T 1 = 4F 1 Rcosα;

[0021]

[0022] F 1 = K 0 Δx;

[0023] T 1 = F 1 Rcosα;

[0024] In the formula, K is 0The rotational stiffness, R represents the distance from the connection point of the helical spring to the steering column, x 0 represents the length of the helical spring when the steering wheel rotates relative to the initial zero position, Δx is the extension of the helical spring, α is the angle between the tension of the helical spring and the tangent of the steering column, F 1 represents the elastic force of a single spring, T 1 is the torque provided by a single spring.

[0025] The beneficial effects of the present invention are:

[0026] Dual redundant design: The switching between the motor force feeling and the mechanical spring force feeling is realized through an electromagnetic clutch. When the road feeling motor fails, it automatically switches to the mechanical redundant mode to ensure that the steering wheel always maintains an effective road feeling feedback, improving the reliability and safety of the system.

[0027] Intelligent steering control: Automatically switches the four-wheel steering mode (out-of-phase / in-phase) according to the vehicle speed to optimize the vehicle handling performance. It provides 9-gear out-of-phase steering at low speeds to improve flexibility and 6-gear in-phase steering at high speeds to enhance stability.

[0028] Safety protection mechanism: Sets a steering wheel rotation angle limit of ±90°. When the threshold is exceeded, it triggers a fixed transmission ratio of the front wheels (i = 9) and a steering limit of ±10° to prevent the risk of oversteering.

[0029] Compact and reliable structure: Integrates components such as an encoder, a damper, and a spring on a fixed bracket, and realizes modular installation through A-type flat keys and bolts, which is convenient for maintenance and has a high space utilization rate.

[0030] Precise force feeling control: The helical spring accurately calculates the additional torque through a trigonometric function model, and superimposes it with the initial torque to form a linearized force feeling feedback characteristic, improving the driver's operation experience. Description of the drawings

[0031] Figure 1 is a cross-sectional view of the redundant device for the steering wheel force feeling of the steer-by-wire system; Figure 2 is a three-dimensional view of the redundant device for the steering wheel force feeling based on the steer-by-wire system;

[0032] Figure 3 is the disassembly of the redundant device for the steering wheel force feeling of the steer-by-wire system Figure 1 ;

[0033] Figure 4 is the disassembly of the redundant device for the steering wheel force feeling of the steer-by-wire system Figure 2 ;

[0034] Figure 5 is the disassembly of the redundant device for the steering wheel force feeling of the steer-by-wire system Figure 3 ;

[0035] Figure 6Disassembly of the Steering Wheel Force Feedback Redundancy Device for Steer-by-Wire Figure 4 ;

[0036] Figure 7 Structural block diagram of the steering wheel force feedback redundancy control strategy for steer-by-wire;

[0037] Figure 8 Schematic diagram of out-of-phase steering when the electromagnetic clutch is energized and the speed < 40 km / h;

[0038] Figure 9 Schematic diagram of in-phase steering when the electromagnetic clutch is energized and the speed ≥ 40 km / h;

[0039] Figure 10 Schematic diagram of front-wheel steering when the electromagnetic clutch is de-energized.

[0040] Figure 11 Schematic diagram of front-wheel steering when the mechanical force feedback and the motor force feedback fail and the encoder recognizes that the steering wheel has turned more than ±90°.

[0041] In the drawings: 1. Nut; 2. Steering wheel; 3. Deep groove ball bearing; 4. Snap ring; 5. Rotational damper fixing bolt; 6. Rotational damper; 7. Spring connection ring; 8. Tightening nut; 9. Electromagnetic clutch mounting bolt; 10. Type A flat key; 11. Road feel motor; 12. Reducer; 13. Steering column; 14. Encoder; 15. Fixing bracket; 16. Spring fixing bolt; 17. Helical spring; 18. Bracket; 19. Washer; 20. Electromagnetic clutch. Detailed implementation manners

[0042] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] As Figures 1 to 6 shown, a steering wheel force feedback redundancy device for steer-by-wire mainly includes a steering wheel 2, a steering column 13, an encoder 14, a fixing bracket 15, a deep groove ball bearing 3, a rotational damper 6, a gasket, a helical spring 17, a set nut 1, a spring 17 connection ring 7, a bracket 18, a Type A flat key 10, an electromagnetic clutch 20, a reducer 12 and a road feel motor 11.

[0044] The steering wheel 2 and the steering column 13 are connected by bolts. The positioning hole of the steering wheel 2 passes through the steering column 13 and is tightened with a nut 81 after positioning to be fixed on the upper part of the steering column 13. When the driver turns the steering wheel 2, the steering column 13 can be driven to rotate. The steering column 13 is machined with a shoulder positioning, a snap ring groove, a hexagonal shaft, a thread and a type A keyway, corresponding to the installation positions of the encoder 14, the deep groove ball bearing 3, the rotary damper 6, the helical spring 17, the deep groove ball bearing 3, the type A flat key 10 and the electromagnetic clutch 20 respectively.

[0045] The encoder 14 passes through the steering column 13 and the housing is fixed on the fixing bracket 15 by bolts. The inner ring of the encoder 14 and the steering column 13 are fixed to keep the relative position unchanged. When the steering column 13 rotates, the encoder 14 can identify the angular signal and the steering speed.

[0046] The fixing bracket 15 is provided with fixing bracket 15 mounting holes and is fixed on the vehicle frame by bolts to keep the relative position with the vehicle frame unchanged. The fixing bracket 15 is provided with an encoder mounting hole and a damper mounting hole at the upper part. The encoder fixing bolt passes through the encoder mounting hole and is screwed into the nut to fix the position. The rotary damper 6 is installed on the fixing bracket 15 by bolts. The fixing bracket 15 is internally provided with a bearing mounting hole, and the deep groove ball bearing 3 is installed on the fixing bracket 15 and the steering column 13 to realize bearing positioning. There are 8 threaded holes on the lower circumference of the fixing bracket 15 for installing 4 helical springs 17 and the bracket 18.

[0047] The housing of the rotary damper 6 is installed inside the fixing bracket 15 through two positioning mounting holes, and the inner ring transmits the rotary motion with the steering column 13 through a hexagonal hole. When the driver turns the steering wheel 2 to drive the steering column 13 to rotate, the rotary damper 6 generates a damping force, and the damping of the rotary damper 6 can be adjusted before installation.

[0048] The helical spring 17 is provided with hook rings at both ends. During the installation process, one end of the helical spring 17 is hooked to the spring connection ring 7, and the other end is hooked to the bolt rotated to the fixing bracket 15.

[0049] The inner hole of the spring connection ring 7 is a threaded hole, and 4 small round holes are provided in the circumferential direction. The adjusting gasket and the tightening nut 8 can adjust the height of the spring connection ring 7 relative to the circular plane of the fixing bracket 15, so as to realize the adjustment of the pre-tightening force of the spring 17 during installation.

[0050] The bracket 18 is fixed on the circular plane of the fixing bracket 15 by bolts through four bracket mounting holes. There are four electromagnetic clutch 20 mounting holes at the upper part of the bracket 18, and a deep groove ball bearing mounting hole inside. The mounting hole and the shoulder of the steering column 13 realize the positioning of the deep groove ball bearing 3.

[0051] The electromagnetic clutch 20 is mounted on the bracket 18 by bolts through 4 electromagnetic clutch mounting holes evenly distributed in the circumferential direction. Key grooves are provided at both ends of the electromagnetic clutch 20. The end of the steering column 13 is driven by the electromagnetic clutch 20 through a flat key A 10. The output end of the speed reducer 12 is driven by the electromagnetic clutch 20 through a flat key A 10. When the electromagnetic clutch 20 is energized, the steering column 13 and the output shaft of the speed reducer 12 are driven. When powered off, the speed reducer 12 and the steering column 13 are not driven, that is, the rotational movement of the steering column 13 is not affected by the output shaft of the speed reducer 12.

[0052] As Figure 7 shown, a redundant control strategy for the steering wheel force feeling of steer-by-wire, which is used to control the redundant device for the steering wheel force feeling of steer-by-wire. The control strategy includes:

[0053] Step 1: Real-time collect the steering wheel angle θ and steering speed signal through the encoder, and transmit them to the vehicle controller (VCU). The vehicle controller distributes the steering wheel angle according to the vehicle speed and steering speed signal;

[0054] For a steer-by-wire vehicle, the steering wheel angle can be set to ±90° compared with a traditional vehicle. During the installation process, the steering damping C 0 , stiffness K 0 , and initial steering torque T 0 of the steering wheel are determined according to different steering force feeling requirements. Select the corresponding damper, helical spring and adjusting spring connection ring. Input these parameters into the motor control algorithm, and the motor outputs the rotational damping C, rotational stiffness K and rotational torque T.

[0055] When the steering wheel rotates, the encoder outputs the steering angle and steering speed signal. The VCU distributes the steering angle of each steering wheel according to the signal of the encoder. After receiving the steering angle signal from the VCU, the steering motor controller drives the wheels to steer. At the same time, the VCU outputs a signal to control the output state of the road feeling motor, and the road feeling motor feeds back information such as the bus current, motor torque and the position of the motor's own encoder to the VCU.

[0056] Step 2: Monitor the bus current, torque and encoder position of the road feeling motor through the vehicle controller, set the monitoring standard. If the monitoring result of the vehicle controller exceeds the monitoring standard, control the electromagnetic clutch to disconnect;

[0057] When the VCU loses communication with the road feeling motor, the VCU controls the electromagnetic clutch to disconnect.

[0058] When the VCU monitors that the bus current of the road feeling motor is too large, the VCU controls the electromagnetic clutch to disconnect.

[0059] When the VCU detects that the positions of the encoders of the road feel motor and the steering wheel differ by 1°, the VCU controls the electromagnetic clutch to disengage.

[0060] When the VCU detects that the torque of the road feel motor is too large, the VCU controls the electromagnetic clutch to disengage.

[0061] Step 3: When the electromagnetic clutch is energized, the road feel motor and the helical spring jointly provide superimposed damping, rotational stiffness, and rotational torque, and select the steering mode according to the vehicle speed;

[0062] Analyze the force on a single helical spring. When the steering wheel angle is θ, the distance from the spring connection point to the steering column = R, and the length of the helical spring when the steering wheel rotates relative to the initial zero position = x 0 , the spring extension The included angle between the spring tension and the tangent of the steering column The elastic force F of a single spring 1 = K 0 Δx, the torque T provided by a single spring 1 = F 1 Rcosα.

[0063] So when the steering wheel angle is θ, the torque provided by the helical spring

[0064] When the electromagnetic clutch is energized, the steering column and the output shaft of the reducer are connected for motion transmission, that is, the damping transmitted to the steering wheel is C-C 0 , the rotational stiffness is K-K 0 , the rotational torque is T-(T 0 +T ′ ).

[0065] When the damping of the steering wheel is C-C 0 , the rotational stiffness is K-K 0 , the rotational torque is T-(T 0 +T ′ ), the simulated road feel of the motor and the mechanical simulated road feel are superimposed on each other, the steering wheel end of the steer-by-wire system works normally, and at this time, the distributed drive performs four-wheel steering and travels along a non-Ackermann steering trajectory.

[0066] As Figure 8 shown, when the vehicle speed < 40 km / h, the vehicle performs out-of-phase four-wheel independent steering. According to the different radii of the steering circles formed by the four steering wheels, the out-of-phase steering is divided into 9 gears, which respectively correspond to the steering states where the inner steering wheels rotate 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°.

[0067] The VCU receives the output torque signal of the road feel motor every 20 ms, and records the output torque difference of the road feel motor within every 20 ms as ΔT. According to the ratio k 0 of ΔT to the initial steering torque T 0 、k 1 、k 2 、k 3 、k 4 、k 5 、k 6 、k 7 、k 8 , it corresponds to 9 steering states of out-of-phase steering when the vehicle speed v < 40 km / h.

[0068] As Figure 9 shown, when the vehicle speed ≥ 40 km / h, the vehicle performs in-phase four-wheel independent steering. According to the steering magnitude of in-phase four-wheel steering, the in-phase steering is divided into 6 gears, which respectively correspond to the steering states of the steering angles of 0°, 2°, 4°, 6°, 8°, and 10° of in-phase four-wheel steering.

[0069] The VCU receives the output torque signal of the road feel motor every 20 ms, and records the output torque difference of the road feel motor within every 20 ms as ΔT'. According to the ratio k 0 of ΔT' to the initial steering torque T ′ 0 、k ′ 1 、k ′ 2 、k ′ 3 、k ′ 4 and k ′ 5 , it corresponds to 6 steering states of out-of-phase steering when the vehicle speed v ≥ 40 km / h.

[0070] Step 4: When the electromagnetic clutch is powered off, mechanical road feel is provided according to the steering wheel force sense redundancy device, four-wheel steering is turned off, the rear wheels return to zero, and the front wheels perform Ackerman steering with a fixed transmission ratio, that is, as Figure 10 shown;

[0071] When the electromagnetic clutch is powered off, the steering column and the output shaft of the reducer are disconnected and power transmission cannot be carried out. The damping of the steering wheel is C 0 、the rotational stiffness is K 0 、the rotational torque is T 0 +T ′ .

[0072] The four-wheel steering function of the vehicle is turned off. After the last four-wheel steering adjustment, the rear-wheel steering motor returns to the zero steering angle position. Only the front wheels are steered, and Ackermann steering is performed with a fixed transmission ratio of i = 3. That is, when the steering wheel is turned 90°, the front inner steering wheel is turned 30°.

[0073] As Figure 11 shown, when the encoder recognizes that the steering angle of the steering wheel is greater than ±90°, both the mechanical road feel and the motor road feel fail. The VCU turns off the rear-wheel steering and the large-angle front-wheel steering, and changes the fixed transmission ratio i ′ = 9, and when the encoder recognizes that the steering angle of the steering wheel exceeds ±90°, the VCU takes the steering wheel angle as ±90°, and the front-wheel steering is 10°.

[0074] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0075] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

[0076] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A steering wheel force sense redundancy device for steer-by-wire, comprising a steering wheel and a steering column, wherein the steering wheel and the steering column are fixed by bolts to form a rotation transmission structure, characterized in that: The device also includes: The steering column is provided with a shaft shoulder positioning, a circlip groove, a hexagonal shaft, a thread line and an A-type keyway, which are respectively used to install an encoder, a deep groove ball bearing, a rotary damper, a spiral spring, a deep groove ball bearing, an A-type flat key and an electromagnetic clutch; A fixing frame is also fixedly arranged on the frame, and the fixing frame is used to provide support for the encoder, the rotary damper, the deep groove ball bearing and the spiral spring; The rotary damper is connected to the steering column through a hexagonal hole to provide basic damping, and the steering column is driven by an A-type flat key and an electromagnetic clutch; The coil spring is connected to the fixing frame through a spring connecting ring to provide redundant mechanical road feel; The deep groove ball bearing is used to provide rotational support for the steering column and the fixed frame; The end of the steering column and the electromagnetic clutch are driven by an A-type flat key, and the output end of the reducer is driven by the electromagnetic clutch through an A-type flat key. When the electromagnetic clutch is powered on, the steering column and the output shaft of the reducer are driven; The electromagnetic clutch is disconnected by the vehicle controller when the road sensing motor fails, so that the steering column is separated from the reducer.

2. A steering wheel force redundancy control strategy for steer-by-wire, used to control the steering wheel force redundancy device for steer-by-wire, characterized in that: The control strategy includes: Step 1: The steering wheel angle θ and steering speed signal are collected in real time by an encoder and transmitted to the vehicle controller, and the vehicle controller allocates the steering wheel angle according to the vehicle speed and steering speed signal; Step 2: Monitor the bus current, torque and encoder position of the road sensing motor through the vehicle controller, set the monitoring standard, and if the monitoring result of the vehicle controller exceeds the monitoring standard, control the electromagnetic clutch to disconnect; Step 3: When the electromagnetic clutch is powered on, the road sensing motor and the coil spring jointly provide superimposed damping, rotational stiffness and rotational torque, and select a steering mode according to the vehicle speed; Step 4: When the electromagnetic clutch is powered off, the steering wheel force sense redundancy device provides mechanical road sense, the four-wheel steering is turned off, the rear wheels return to zero, and the front wheels use a fixed transmission ratio to perform Ackerman steering; If the steering wheel angle exceeds ±90°, the protection mechanism is triggered; The mechanical road feel is calculated based on the steering wheel angle θ to calculate the additional torque T′ provided by the coil spring, and is superimposed with the initial torque T0 to obtain the total torque, where: T′=4T1=4F1Rcosα; F1=K0Δx; T1=F1Rcosα; Where K0 is the rotational stiffness, R is the distance from the connection point of the coil spring to the steering column, x0 is the length of the coil spring when the steering wheel is initially in zero position, Δx is the extension of the coil spring, α is the tangential angle between the coil spring tension and the steering column, F1 is the elastic force of a single spring, and T1 is the torque provided by a single spring.

3. The steering wheel force redundancy algorithm according to claim 2 is characterized in that: The monitoring standards include: Road sensor motor communication is lost; The bus current exceeds the threshold; The position deviation between the road sense motor and the steering wheel encoder is greater than 1°; The torque exceeds the threshold.

4. The steering wheel force redundancy algorithm according to claim 2 is characterized in that: The protection mechanism includes: The front wheel steering limit is ±10°, the transmission ratio is adjusted to 9, and the vehicle controller forces the steering wheel angle to be ±90°.

5. The steering wheel force redundancy algorithm according to claim 2, characterized in that: In step 1, when the vehicle speed is less than 40 km / h, the vehicle controller controls the four-wheel out-of-phase steering, which is divided into 9 gears. The inner steering wheel angles are 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, and 40°, respectively, and the corresponding road sense motor output torque difference ΔT accounts for the ratio of the initial torque T0 k0, k1, k2, k3, k4, k5, k6, k7, and k8.

6. The steering wheel force redundancy algorithm according to claim 2, characterized in that: When the vehicle speed is ≥40km / h, the vehicle controller controls the four-wheel out-of-phase steering, which is divided into 6 gears. The inner steering wheel angles are 0°, 2°, 4°, 6°, 8°, and 10°, respectively. The corresponding ratios of the road sense motor output torque difference ΔT′ to the initial torque T0 are k′0, k′1, k′2, k′3, k′4, and k′5.

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