A rear wheel steering modeling method

Abstract

The application discloses a rear wheel steering modeling method in ADAMS, which comprises the following steps: newly establishing a rear wheel steering system rack and a rear wheel steering system rack shell component, establishing a fixed pair between the rack shell and a subframe, establishing a moving pair along the rack axis between the rack and the rack shell, and adding a drive on the moving pair; newly establishing a connected component; when the rear wheel steering system is activated, the connected component should select the steering system rack; when the rear wheel steering system is not activated, the connected component should select the subframe; the rear suspension steering modeling simulation and the whole vehicle four-wheel steering modeling simulation can be performed in ADAMS; the rear suspension steering simulation and the whole vehicle four-wheel steering simulation can be performed in ADAMS by activating the rear wheel steering system and controlling the rear wheel angle ratio; meanwhile, the rear wheel steering system can be not activated, the rear suspension system without the rear wheel steering can be simulated without influence, and the rear suspension template can still be kept universal.

Description

Technical Field

[0001] This invention relates to the field of automotive steering system technology, and in particular to a rear-wheel steering modeling method. Background Technology

[0002] The steering system is a crucial component of a vehicle's chassis. Drivers use the steering wheel to direct the vehicle in a designated direction, making the steering system vital for driving safety. Current front-wheel steering systems primarily consist of the steering wheel, steering column, steering gear, and steering tie rods. The driver applies input to the steering wheel, which is transmitted through the steering column to the steering gear. The rack in the steering gear then drives the steering tie rods, ultimately steering the wheels. Generally, when a vehicle is making a U-turn or reversing at low speeds, the wheel angles are larger to reduce the turning radius and improve maneuverability. Conversely, at high speeds, the wheel angles are smaller to ensure vehicle safety.

[0003] With economic development, car ownership is increasing, and consumers are demanding higher quality vehicles, with a greater need for interior space. This has led to a significant increase in vehicle wheelbase and track width. However, this increase also brings some inconveniences, primarily a larger minimum turning diameter. Due to space constraints in wheel arrangement, the turning angle cannot be continuously increased; the inner wheel turning angle is generally limited to around 40 degrees. The increased wheelbase and track width result in a larger minimum turning diameter, worsening vehicle passability and significantly reducing the ease of U-turns. Simultaneously, the increased wheelbase also impacts vehicle handling stability. For these reasons, with the rapid development of electronic technology, rear-wheel steering systems have emerged. A rear-wheel steering system adds a steering system to the rear suspension without altering the existing front-wheel steering system. Typically, the rear suspension's toe-in link and subframe connection point are disconnected and connected to the steering rack. Suspensions suitable for adding a rear-wheel steering system cannot have trailing arms; five-link suspensions and H-arm suspensions are more suitable.

[0004] Rear-wheel steering systems allow the rear wheels to turn in the opposite direction to the front wheels at low speeds, reducing the turning diameter and improving maneuverability when parking, making U-turns, or navigating tight spaces. At high speeds, the rear-wheel steering system allows the rear wheels to turn in the same direction as the front wheels, significantly reducing the vehicle's sideslip angle and improving high-speed stability. In recent years, rear-wheel steering systems have matured and become more affordable, leading to their adoption in mid-range and lower-end markets. Therefore, modeling and simulation research of rear-wheel steering systems is becoming increasingly important. ADAMS is the most commonly used tool for vehicle chassis dynamics simulation; however, its built-in steering system templates are currently limited to the most common rack and pinion and recirculating ball steering systems (front-wheel steering), and cannot simulate and analyze suspension systems with rear-wheel steering. Therefore, developing a rear-wheel steering system modeling method suitable for automakers is essential and can provide significant technical support for early-stage product development. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a rear-wheel steering modeling method that enables individual rear-wheel steering simulation of the rear suspension and four-wheel steering simulation of the entire vehicle within ADAMS.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] This rear-wheel steering modeling method is implemented in ADAMS, and its methods include:

[0008] A new rear wheel steering system rack and a rear wheel steering system rack housing component are constructed. A fixed pair is established between the rack housing and the subframe, and a sliding pair is established between the rack and the rack housing along the rack axis. A drive is added to the sliding pair.

[0009] Create a new connection component; when the rear-wheel steering system is active, the connection component should be selected as the steering system rack; when the rear-wheel steering system is inactive, the connection component should be selected as the subframe.

[0010] The steering modeling and simulation of the rear suspension and the steering modeling and simulation of all four wheels of the vehicle can be performed in ADAMS.

[0011] Further:

[0012] The newly constructed connecting component can be selected from the toe-in tie rod, the rear wheel steering system rack, and the subframe. At the same time, a ball joint between the toe-in tie rod and the steering knuckle is established at the outer connection point of the toe-in tie rod, and a ball joint between the toe-in tie rod and the adapter is established at the inner point of the toe-in tie rod.

[0013] In the method, control variables for activation and inhibition of the rear wheel steering system and control variables for the ratio of rear wheel to front wheel steering angles are established.

[0014] In the method described, a new control variable is created that includes the rear wheel steering system rack, rack housing, rack housing and subframe fixed joint, rack and rack housing sliding joint, toe-in tie rod inner and outer ball joints, and sliding joint drive. In this way, the rear wheel steering system can be activated through the control variable.

[0015] In the method described, a new state variable function is added to the front suspension to obtain the front wheel steering angle, and a new output communicator for the state variable is also created.

[0016] In the method described, the upper drive of the rack-sliding joint of the rear wheel steering system is modified to provide a constant rack input. Then, a vertical jump simulation without input is performed on the rear suspension. The relationship curve between the rear suspension wheel angle and rack displacement is obtained in the post-processing interface. Returning to the template interface, a new spline for the rear suspension wheel angle and rack displacement is created, and the interpolation function for the wheel angle and rack displacement of the sliding joint drive is edited.

[0017] In the method described, the original inner and outer point connecting bushings of the toe-in rod are retained, and the connecting component of the inner point connecting bushing of the toe-in rod is modified into the toe-in rod and the adapter.

[0018] In the method described, a suppression variable needs to be established to control the suppression of the rear wheel steering system; when the rear wheel steering system is activated, the inner and outer connecting bushings of the toe-in rod are not activated, while the ball joint is activated.

[0019] In the method described, a new input communicator for the state variable is simultaneously created in the rear suspension to transmit the front wheel steering angle to the rear suspension.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This rear-wheel steering modeling method, without altering the original front-wheel steering system template, creates a rack and rack housing in the rear suspension system and establishes component connection relationships. New control variables can activate and deactivate the rear-wheel steering system, as well as control the rear wheel steering angle ratio. In ADAMS, by activating the rear-wheel steering system and controlling the rear wheel steering angle ratio, rear suspension steering simulation and full-vehicle four-wheel steering simulation can be performed. Simultaneously, the rear-wheel steering system can be deactivated without affecting the simulation of the rear suspension system without rear-wheel steering, and the rear suspension template remains universal. Attached Figure Description

[0022] The following is a brief explanation of the contents of each of the accompanying drawings and the markings in the drawings:

[0023] Figure 1 This is a model diagram of the rear five-link suspension with added rear wheel steering system of the present invention.

[0024] Figure 2 This is a simulation diagram of the integrated control of the rear wheel steering system of the present invention.

[0025] In the picture:

[0026] 1. Toe-in strut, 2. Rack housing, 3. Rack, 4. Subframe, 5. Steering knuckle. Detailed Implementation

[0027] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and through the description of the examples.

[0028] like Figure 1 and Figure 2 As shown, this rear-wheel steering system modeling method adds a rear-wheel steering system to the rear suspension system without changing the original front-wheel steering system template. It can realize the independent steering simulation of the rear suspension and the four-wheel steering simulation of the whole vehicle in ADAMS. It can also output the ADAMS whole vehicle dynamics model and Simulink for joint simulation study of the rear-wheel steering system control strategy.

[0029] The specific method of this invention includes:

[0030] 1. Based on the original rear suspension system template, such as a five-link suspension or an H-arm suspension, the following will use a five-link suspension as an example. Create a new rear wheel steering system rack and a rear wheel steering system rack housing component. Establish a fixed joint between the rack housing and the subframe, and establish a sliding joint between the rack and the rack housing along the rack axis. At the same time, add a motion (drive) to the sliding joint.

[0031] 2. Create a new adapter `switch_part` "toelink_connector" (for toe-up tie rod connection). The connectable components should be the toe-up tie rod, rear wheel steering system rack, and subframe. Simultaneously, create a ball joint between the toe-up tie rod and steering knuckle at the outer connection point of the toe-up tie rod, and a ball joint between the toe-up tie rod and the adapter at the inner connection point. Retain the original inner and outer connection bushings of the toe-up tie rod, and modify the connection component of the inner connection bushing to the toe-up tie rod and the adapter. When the rear wheel steering system is active, the component connected to `switch_part` should be the steering system rack; when the rear wheel steering system is inactive, the component connected to `switch_part` should be the subframe. This ensures that the components connected to the toe-up tie rod when it is active or inactive correspond to the actual components.

[0032] 3. Establish the control variable rear_steer_active (rear wheel steering activation) for activating and inhibiting the rear wheel steering system, and the control variable rear_steer_ratio (rear wheel steering ratio) for the ratio of rear wheel to front wheel steering angles.

[0033] 4. Create a new `rear_steer_active` group that includes the rear steering system rack, rack housing, rack housing to subframe fixed joint, rack to rack housing sliding joint, toe-in tie rod inner and outer ball joints, and sliding joint drive motion. This allows the rear steering system to be activated via the variable `rear_steer_active`. Simultaneously, create a `rear_steer_inactive` group to control the suppression of the rear steering system. When the rear steering system is activated, the inner and outer bushings of the toe-in tie rod are inactive, while the ball joint is activated. This is because in a real rear steering system, both the inner and outer points of the toe-in tie rod are ball joints, whereas without a rear steering system, both the inner and outer points are bushing connections.

[0034] 5. Add a new state variable function `front_steer_angle` (front wheel angle) to the front suspension to obtain the front wheel angle. Also, create an output communicator for the state variable `front_steer_angle` (front wheel angle). Simultaneously, create an input communicator for the state variable `front_steer_angle` (front wheel angle) in the rear suspension to transmit the front wheel angle to the rear suspension.

[0035] 6. Modify the Motion function on the rack-slip joint of the rear-wheel steering system, providing a constant rack input. Then, perform a vertical jump simulation on the rear suspension without input. Obtain the curve showing the relationship between the rear suspension wheel angle and rack displacement in the post-processing interface. Return to the template interface, create a new spline for the rear suspension wheel angle and rack displacement, and edit the interpolation function for the wheel angle and rack displacement of the Motion joint, multiplying `rear_steer_active` (rear wheel steering activation), `front_steer_angle` (front wheel angle), and `rear_steer_ratio` (rear wheel angle ratio) by these values.

[0036] At this point, the main content of the rear-wheel steering system modeling is complete. The rear-wheel steering system is activated by setting the value of rear_steer_active to 1 or 0. This allows for rear suspension steering simulation and whole-vehicle four-wheel steering simulation in ADAMS. Alternatively, the vehicle dynamics model can be output to Simulink through the ADAMS control module Control for integrated simulation.

[0037] The present invention has the following advantages:

[0038] 1. Without changing the original front suspension steering system model, simply add a steering system to the rear suspension model. The rear wheel steering system can be activated or deactivated by controlling the variable rear_steer_active (rear wheel steering activation). The rear suspension template can still remain universal.

[0039] 2. By controlling the variable rear_steer_ratio (rear wheel steering angle ratio), the relationship between the rear wheel steering angle and the front wheel steering angle can be controlled. This allows for easy modification of variable values ​​in ADAMS to study the impact of different steering angle ratios on vehicle performance, such as the effect of different rear wheel steering angles on the turning diameter.

[0040] 3. The vehicle dynamics model can be output from the ADAMS Control module to Simulink for integrated simulation, and the impact of different rear-wheel steering control strategies on the vehicle's handling and stability can be studied.

[0041] By outputting the vehicle dynamics model from the ADAMS Control module to Simulink, integrated simulation studies can be performed to investigate the impact of rear-wheel steering control strategies on vehicle handling and stability. Figure 2 As shown, the ADAMS vehicle dynamics model outputs parameters such as vehicle speed, yaw rate, sideslip angle, and front wheel steering angle. The rear wheel steering control strategy calculates the optimal rear wheel steering angle ratio and returns it to the ADAMS vehicle dynamics model. With this complete integrated simulation model built, engineers can independently modify the rear wheel steering control strategy module in Simulink to conduct simulations, study the impact of different strategies on overall vehicle performance, find the optimal control strategy, shorten product development cycles, and accelerate new product development.

[0042] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the concept and technical solution of the present invention, or the direct application of the concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A rear-wheel steering modeling method, characterized in that: The rear-wheel steering modeling method is implemented in ADAMS, and its methods include: A new rear wheel steering system rack and a rear wheel steering system rack housing component are constructed. A fixed pair is established between the rack housing and the subframe, and a sliding pair is established between the rack and the rack housing along the rack axis. A drive is added to the sliding pair. Create a new connection component; when the rear-wheel steering system is active, the connection component should be selected as the rear-wheel steering system rack; when the rear-wheel steering system is inactive, the connection component should be selected as the subframe. Perform steering modeling and simulation of the rear suspension and the four-wheel steering of the whole vehicle in ADAMS; The newly constructed connecting component can be selected as the toe-in tie rod, rear wheel steering system rack, and subframe; at the same time, a ball joint between the toe-in tie rod and the steering knuckle is established at the outer connection point of the toe-in tie rod, and a ball joint between the toe-in tie rod and the adapter is established at the inner point of the toe-in tie rod. In the method described, a new control variable is created that includes the rear wheel steering system rack, rack housing, rack housing and subframe fixed joint, rack and rack housing sliding joint, toe-in tie rod inner and outer ball joints, and sliding joint drive. This allows the rear wheel steering system to be activated through the control variable. At the same time, a suppression variable is also needed to control the suppression of the rear wheel steering system. When the rear wheel steering system is activated, the inner and outer connecting bushings of the toe-in tie rod are not activated, while the ball joint is activated.

2. The rear-wheel steering modeling method as described in claim 1, characterized in that: In the method, control variables for activation and inhibition of the rear wheel steering system and control variables for the ratio of rear wheel to front wheel steering angles are established.

3. The rear-wheel steering modeling method as described in claim 1, characterized in that: In the method described, a new state variable function is added to the front suspension to obtain the front wheel steering angle, and a new output communicator for the state variable is also created.

4. The rear-wheel steering modeling method as described in claim 1, characterized in that: In the method described, the upper drive of the rack-sliding joint of the rear wheel steering system is modified to provide a constant rack input. Then, a vertical jump simulation without input is performed on the rear suspension. The relationship curve between the rear suspension wheel angle and rack displacement is obtained in the post-processing interface. Returning to the template interface, a new spline for the rear suspension wheel angle and rack displacement is created, and the interpolation function for the wheel angle and rack displacement of the sliding joint drive is edited.

5. The rear-wheel steering modeling method as described in claim 1, characterized in that: In the method described, the original inner and outer point connecting bushings of the toe-in rod are retained, and the connecting component of the inner point connecting bushing of the toe-in rod is modified into the toe-in rod and the adapter.

6. The rear-wheel steering modeling method as described in claim 3, characterized in that: In the method described, a new input communicator for the state variable is simultaneously created in the rear suspension to transmit the front wheel steering angle to the rear suspension.

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