Vehicle test system, steering reaction force input device, and steering function evaluation method

Abstract

This invention uses a chassis dynamometer to evaluate a steering function of a vehicle having an automatic steering function or a test piece constituting a portion of the vehicle. A vehicle testing system 100 configured to conduct a driving test of a vehicle having the automatic steering function or the test piece W constituting a portion of the vehicle, comprises: a chassis dynamometer 2 for conducting the driving test of the test piece W; and a steering reaction force inputting device 3 that inputs a steering reaction force to a steering rack gear W4 of the test piece while the test pieces is in a state with a tie rod removed, the vehicle testing system evaluating the steering function of the test piece W by inputting a steering reaction force to the test piece W while the test piece drives on the chassis dynamometer 2.

Description

Technical Field

[0001] The present invention relates to a vehicle test system for conducting a running test on a specimen that is a vehicle or a part thereof having a steering function, a steering reaction force input device for inputting a steering reaction force of the specimen, and a steering function evaluation method for evaluating the steering function of the specimen.

Background Art

[0002] Conventionally, a running test of a vehicle such as a four-wheel automobile may be performed using a chassis dynamometer. As shown in Patent Document 1, this chassis dynamometer includes, for example, a roller on which the front wheels are placed and a dynamometer that applies a load to the roller. Then, the vehicle is evaluated by simulating running of the vehicle on this chassis dynamometer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, for example, the development of vehicles (automated driving vehicles) having an automatic steering function has been in progress, and there is a demand to evaluate such vehicles on a chassis dynamometer.

[0005] However, a conventional chassis dynamometer has a configuration in which the rotation axis of the front wheel roller is fixed and does not allow steering of the vehicle, and thus the steering function cannot be evaluated.

[0006] As shown in Patent Document 2, although a chassis dynamometer with a steering function that allows steering of a vehicle has been considered, in this chassis dynamometer, it is necessary to rotate the roller and the dynamometer, and the device configuration is large-scale and expensive. In addition, since the heavy roller and dynamometer are rotated, there are problems such as in terms of controllability.

[0007] The present invention has been made in view of the above-described problems, and its main object is to evaluate the steering function of a test specimen that is a vehicle having a steering function or a part thereof on a chassis dynamometer.

Means for Solving the Problems

[0008] That is, a vehicle test system according to the present invention is a vehicle test system for performing a running test on a test specimen that is a vehicle having a steering function or a part thereof, and includes a chassis dynamometer for performing a running test on the test specimen, and a steering reaction force input device for inputting a steering reaction force to a steering rack gear of the test specimen running on the chassis dynamometer.

[0009] With such a vehicle test system, by inputting a steering reaction force to the steering rack gear of the test specimen, while keeping the wheels of the test specimen in a straight-ahead running state and running the test specimen on the chassis dynamometer, the steering function of the test specimen can be evaluated. Further, in the present invention, since the steering reaction force is directly input to the steering rack gear without using a chassis dynamometer with a steering function, it has an inexpensive configuration and can improve the controllability of the steering reaction force.

[0010] As a specific installation mode of the steering reaction force input device, it is desirable that the steering reaction force input device is connected to the steering rack gear and the tie rod end link via an attachment. With this configuration, by making the attachment corresponding to each vehicle, it is possible to correspond to various test specimens without changing the basic configuration of the steering reaction force input device.

[0011] Here, when the test specimen runs on the chassis dynamometer, the steering rack gear of the test specimen and the tie rod end link move relatively up and down. Therefore, in the case of a configuration in which the steering reaction force input device is connected between the steering rack gear and the tie rod end link, it is desirable that the steering reaction force input device has an absorption structure that absorbs the relative vertical movement of the steering rack gear and the tie rod end link.

[0012] In the case of a configuration in which the steering reaction force input device is connected between the steering rack gear and the tie rod end link, the response characteristics of the steering rack gear change due to the self-weight of the steering reaction force input device. In order to reduce the influence on the response characteristics of the steering rack gear, it is desirable that the steering reaction force input device has a support mechanism that supports its own weight against the floor.

[0013] In order to input the steering reaction force to the steering rack gear with a simple configuration, it is desirable that the steering reaction force input device inputs the steering reaction force to the steering rack gear of the test specimen via a steering wheel or a steering shaft.

[0014] As a specific embodiment of the steering reaction force input device, it is conceivable that the steering reaction force input device includes an actuator that generates the steering reaction force, a load cell that detects the steering reaction force applied to the steering rack gear by the actuator, and a steering reaction force control unit that feedback-controls the actuator using the detection signal of the load cell.

[0015] In a vehicle, there is a dead zone of steering due to tire torsional deformation, play in the steering system, etc. In order to reproduce this dead zone, it is desirable that the steering reaction force input device has an elastic body element (such as a rubber bush, a spring, etc.) that reproduces the dead zone associated with steering.

[0016] In order to accurately adjust the input steering reaction force over a wide range with a simple configuration, it is desirable that the steering reaction force input device includes a first actuator that generates a low-frequency and large-stroke steering reaction force and a second actuator that generates a high-frequency and small-stroke steering reaction force.

[0017] It is desirable that the steering reaction force input device includes a release mechanism that releases the steering reaction force applied to the steering rack gear when the steering force applied from the steering of the specimen reaches a predetermined threshold value. With this configuration, the steering reaction force input device can be protected.

[0018] It is desirable that the vehicle test system of the present invention further includes a driving robot that automatically drives the specimen. By performing a running test on the specimen with the driving robot, it is possible to suppress driving variations and perform a high-precision running test compared to the case where a person drives.

[0019] As a specific embodiment of the steering reaction force control unit that controls the actuator, it is desirable that the steering reaction force control unit calculates a command value for the actuator from a vehicle speed signal indicating the vehicle speed of the specimen or a steering angle signal indicating the steering angle of the specimen, and controls the actuator based on the command value.

[0020] Here, in order to input the steering reaction force due to the self-aligning torque and evaluate the steering function, it is desirable that the steering reaction force control unit calculates the self-aligning torque from the steering angle signal and calculates the command value based on the self-aligning torque.

[0021] Further, in order to input the steering reaction force at low speeds and during parking and evaluate the steering function, it is desirable that the steering reaction force control unit calculates the command value for the actuator at low speeds and during parking from a vehicle speed signal indicating the vehicle speed of the specimen.

[0022] In order to evaluate the steering function by inputting a steering reaction force independent of the vehicle model, it is desirable for the steering reaction force control unit to calculate a command value for the actuator based on a vehicle abnormality, a road surface change, or other disturbances. (1) Vehicle abnormality: misalignment of the steering system, one-sided flow, tire differential friction, etc. (2) Road surface change: ice burn, μ jump (change in adhesive resistance between the tire and the road surface), etc. (3) Other disturbances: undulation, crosswind, one-sided gradient, rough road, curb contact, wheel detachment, etc.

[0023] In order to evaluate the steering function by inputting a steering reaction force due to a posture change caused by vertical movement, it is desirable for the steering reaction force control unit to calculate a command value for the actuator based on the steering reaction force generated by the vertical posture change of the specimen.

[0024] In order to evaluate the steering function by inputting a steering reaction force accompanying left and right load transfer during turning, it is desirable for the steering reaction force control unit to calculate a command value for the actuator based on the steering reaction force generated by the posture change of the specimen during turning.

[0025] In order to perform a running test considering the change in rolling resistance due to load transfer during turning by linking the steering reaction force input device and the chassis dynamometer, the dynamometer control unit that controls the chassis dynamometer calculates the moving load generated during turning of the specimen, calculates the rolling resistance of the left and right wheels or the front and rear wheels due to the moving load, and based on the rolling resistance, it is desirable to calculate the load command value of the chassis dynamometer. With this configuration, the specimen can be evaluated in a state close to actual running (actual environment).

[0026] In order to evaluate the steering function by inputting a steering reaction force due to a posture change during braking or acceleration, it is desirable for the steering reaction force control unit to calculate a command value for the actuator based on the change in the steering reaction force generated by the posture change of the specimen during braking or acceleration.

[0027] When the vehicle suddenly brakes during actual driving, an inertial force acts on the vehicle. However, when the vehicle suddenly brakes while driving on a chassis dynamometer, no inertial force acts on the vehicle. Also, the deceleration during driving on a chassis dynamometer is obtained by differentiating the vehicle speed of the vehicle. However, during sudden braking, the vehicle wheels lock, and it is assumed that the rollers of the chassis dynamometer continue to rotate. Therefore, the deceleration cannot be calculated. Therefore, in order to evaluate the steering function by inputting the steering reaction force due to the attitude change during sudden braking, it is desirable that the steering reaction force control unit calculates a command value to the actuator based on the change in the steering reaction force caused by the attitude change due to the maximum acceleration calculated from the specifications of the test specimen without using the vehicle speed signal indicating the vehicle speed of the test specimen when the test specimen suddenly brakes.

[0028] Further, the steering reaction force input device according to the present invention evaluates the steering function of a test specimen that is an autonomous driving vehicle or a part thereof on a chassis dynamometer, and is characterized in that a steering reaction force is applied to the steering rack gear of the test specimen based on the steering angle and vehicle speed of the test specimen.

[0029] Furthermore, the steering function evaluation device according to the present invention evaluates the steering function of a test specimen that is an autonomous driving vehicle or a part thereof on a chassis dynamometer, and is characterized in that the test specimen is driven on the chassis dynamometer with the wheels of the test specimen in a straight-ahead driving state, and the steering function of the test specimen is evaluated by inputting a steering reaction force to the steering rack gear of the test specimen.

Advantages of the Invention

[0030] According to the present invention described above, the steering function of a test specimen that is a vehicle having an automatic steering function or a part thereof can be evaluated on a chassis dynamometer.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

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Explanation of symbols

[0032] 100 ··· Vehicle test system W ··· Specimen W4 ··· Steering rack gear W5 ··· Tie rod end link 2 ··· Chassis dynamometer 25 ··· Dynamometer control unit 4 ··· Driving robot 3 ··· Steering reaction force input device 31 ··· Actuator 32 ··· Load cell 33 ··· Steering reaction force control unit 39 ··· Absorbing structure 36 ··· Elastic body element 37 ··· Support mechanism 38 ··· Release mechanism 311 ··· First actuator 312 ··· Second actuator

Mode for Carrying Out the Invention

[0033] Hereinafter, a vehicle test system according to an embodiment of the present invention will be described with reference to the drawings.

[0034] The vehicle test system 100 of the present embodiment evaluates the steering function of the steering system of a test specimen W which is a vehicle or a part thereof having a steering function.

[0035] In the following, a complete vehicle of an autonomous vehicle will be described as an example of the test specimen W. However, it is not limited to a complete vehicle as long as it has an automatic steering function and can run on a chassis dynamometer. Further, the test specimen may be a vehicle without an automatic steering function.

[0036] <1. System Configuration> Specifically, as shown in FIG. 1, the vehicle test system 100 includes a chassis dynamometer 2 for conducting a running test on the test specimen W, and a steering reaction force input device 3 for inputting a steering reaction force to the steering rack gear W4. The steering reaction force is input to the test specimen W running on the chassis dynamometer 2 to evaluate the steering function of the test specimen W.

[0037] The chassis dynamometer 2 includes a front-wheel roller 21 on which the front wheel W1 of the test specimen W is placed, a rear-wheel roller 22 on which the rear wheel W2 of the autonomous vehicle W is placed, and dynamometers 23 and 24 that input loads to the front-wheel roller 21 and the rear-wheel roller 22, respectively. Note that a predetermined load command value based on, for example, a predetermined driving pattern is input from the dynamometer control unit 25 to the dynamometers 23 and 24, and they are feedback-controlled. When the test specimen is a front-wheel drive vehicle, it may not have the rear-wheel roller 22 and the dynamometer 24.

[0038] Here, on the test specimen W (autonomous vehicle) placed on the chassis dynamometer 2, a driving robot 4 is mounted on the seat W3 of the driver's seat. This driving robot 4 has various actuators for operating the steering wheel, accelerator, brakes, etc., as needed. Note that the test specimen W is basically under steering control, adaptive cruise control, and automatic braking control by an ADAS (Advanced Driver-Assistance Systems) controller built into the test specimen W or an AD (Autonomous Driving) controller, which is an advanced form of ADAS. Note that instead of using the driving robot 4, a person may drive it, or it may be an unmanned autonomous vehicle.

[0039] Since the test specimen W placed on the chassis dynamometer 2 is an autonomous vehicle, it is equipped with various sensors (cameras, radars, lidars, sonars, GPAs, etc.) for acquiring the surrounding situation. To make this autonomous vehicle run on the chassis dynamometer 2, the vehicle test system 100 is equipped with various emulators 200 for deceiving each of these sensors. Then, the test specimen W placed on the chassis dynamometer 2 is automatically driven by the ADAS controller or the AD controller based on the information or signals input by the various emulators 200.

[0040] As shown in Fig. 2, the steering reaction force input device 3 inputs a steering reaction force to the steering rack gear W4 of the test specimen in a state where the steering force of the steering system is not transmitted to the wheel W1 (here, the state where the tie rod is removed). The steering reaction force input device 3 of the present embodiment is connected to the steering rack gear W4 and the tie rod end link W5. The tie rod end link W5 is connected to the steering knuckle W6 fixed to the front wheel W1. Further, the front wheel W1 with the tie rod removed is rotatable on the chassis dynamometer 2 and is fixed by a steering fixing mechanism 5 using, for example, a free hub or the like so as not to steer.

[0041] Specifically, as shown in Figs. 2 and 3, the steering reaction force input device 3 includes an actuator 31 that generates a steering reaction force, a load cell 32 that detects the steering reaction force applied to the steering rack gear W4 by the actuator 31, and a steering reaction force control unit 33 that performs feedback control on the actuator 31 using the detection signal of the load cell 32. In the present embodiment, the actuator 31 and the load cell 32 are provided at both ends of the steering rack gear W4, respectively.

[0042] The actuator 31 uses, for example, a hydraulic cylinder, a pneumatic cylinder, an electromagnetic solenoid, or an electric motor, and the movable member 31b is configured to move forward and backward with respect to the actuator body 31a.

[0043] For example, in the case of a hydraulic cylinder and a pneumatic cylinder, a piston rod, which is the movable member 31b, moves forward and backward with respect to the cylinder body (actuator body 31a), whereby a steering reaction force is input to the steering rack gear W4. In the case of an electromagnetic solenoid, a plunger, which is the movable member 31b, moves forward and backward with respect to the solenoid coil (actuator body 31a), whereby a steering reaction force is input to the steering rack gear W4. In the case of an electric motor, a ball screw mechanism is connected to the electric motor, and a ball screw nut, which is the movable member 31b, moves forward and backward with respect to the ball screw (actuator body 31a), whereby a steering reaction force is input to the steering rack gear W4.

[0044] In the present embodiment, as shown in FIG. 3, the movable member 31b is connected to the steering rack gear W4 side, and the actuator body 31a is connected to the tie rod end link W5 side. Here, the movable member 31b is connected to the first link member 34, and the first link member 34 is connected to the steering rack gear W4. Further, the actuator body 31a is connected to the second link member 35, and the second link member 35 is connected to the tie rod end link W5. Note that the first link member 34 or the second link member 35 may be configured to be telescopic so that the length can be adjusted according to the distance between the steering rack gear W4 and the tie rod end link W5.

[0045] Further, as shown in FIG. 3, the steering reaction force input device 3 of the present embodiment may include an elastic body element 36 that reproduces a dead zone associated with steering. This elastic body element 36 is provided independently of the feedback control of the actuator 31 and is provided in series with the actuator 31, that is, between the actuator 31 and the steering rack gear W4 or between the actuator 31 and the tie rod end link W5. As this elastic body element 36, for example, a rubber bush, a spring, or the like can be used. Note that the elastic body element 36 may be incorporated in the actuator 31.

[0046] Further, the steering reaction force input device 3 may have an absorption structure 39 that absorbs the relative vertical movement of the steering rack gear W4 and the tie rod end link W5. In this embodiment, the tie rod end link W5 is used, but a link joint structure equivalent to a tie rod may be provided.

[0047] Furthermore, as shown in FIG. 3, the steering reaction force input device 3 may have a support mechanism 37 that supports its own weight with respect to the floor. This support mechanism 37 supports with a reaction force that cancels the weight of the actuator 31 while absorbing the vertical movement of the actuator 31, and can be configured using, for example, a spring or the like. Since the actuator 31 also moves vertically, the movable member 31b of the actuator 31 is configured to be strokeable while absorbing the play angle with respect to the actuator body 31a.

[0048] Moreover, as shown in FIG. 3, the steering reaction force input device 3 may be provided with a release mechanism 38 that releases the steering reaction force applied to the steering rack gear W4 when the steering force applied from the steering system of the specimen W reaches a predetermined threshold value. This release mechanism 38 has, for example, a fixing pin 381 made of resin that fixes the first element 341 on the steering rack gear W4 side that constitutes the first link member 34 and the second element 342 on the actuator 31 side. When the steering force reaches a predetermined threshold value, the fixing pin 381 is cut, and the first element 341 is configured to be relatively movable with respect to the second element 342. Also, a stopper 382 may be provided so that the second element 342 does not move toward the actuator side from a predetermined position so that the stroke amount of the second element 342 does not exceed the allowable stroke amount of the actuator 41.

[0049] <2. Control Content> Next, a specific example of the steering input by the steering reaction force input device 3 of this embodiment will be described.

[0050] As shown in Fig. 2, the steering reaction force control unit 33 calculates a command value for the actuator 31 from a vehicle speed signal indicating the vehicle speed of the test specimen W or a steering angle signal indicating the steering angle of the test specimen W, and controls the actuator 31 based on the command value. In the present embodiment, the steering reaction force control unit 33 includes a command value calculation unit 33a that calculates a command value for the actuator 31, and an actuator drive unit 33b that controls the actuator 31 based on the command value.

[0051] Here, the vehicle speed signal may be obtained from an in-vehicle diagnostic device (OBDII; On-Board Diagnostics second generation) or the like via the CAN (Controller Area Network) of the test specimen W, or may be calculated from the rotational speed of the front wheel roller 21 of the chassis dynamometer 2, or may be calculated from the rotational speed of the front wheel W1 that rotates together with the front wheel roller 21. Further, the steering angle signal may be obtained from the OBDII via the CAN of the test specimen W, or may be calculated from the detection signal of the position sensor 6 that detects the position of a member that moves with steering such as the steering rack gear W4.

[0052] Next, specific control modes will be individually described. Note that the actuator 31 may be controlled by combining two or more of the following control modes.

[0053] (1) Input of steering reaction force by self-aligning torque When the test specimen W turns, the steering reaction force control unit 33 calculates the self-aligning torque from the steering angle signal, calculates a command value based on the self-aligning torque and the detection signal of the load cell 32, and performs feedback control of the actuator 31 based on the command value. Here, the self-aligning torque can be calculated from the relationship between the slip angle [deg] and the wheel load [kg] and the like. Note that data indicating the relationship between the slip angle [deg] and the calculated self-aligning torque [Nm] is pre-recorded in the data storage unit 33c of the steering reaction force control unit 33.

[0054] (2) Input the steering reaction force during parking and at low speeds During low speeds and parking (when stationary), the steering reaction force control unit 33 calculates the steering reaction force from the vehicle speed signal, calculates a command value based on the steering reaction force and the detection signal of the load cell 32, and performs feedback control of the actuator 31 based on the command value.

[0055] (3) Input a steering reaction force independent of the vehicle model The steering reaction force control unit 33 calculates the steering reaction force based on the following: (a) vehicle abnormalities, (b) road surface changes, or (c) disturbances other than these, calculates a command value based on the steering reaction force and the detection signal of the load cell 32, and performs feedback control of the actuator 31 based on the command value. (a) Vehicle abnormalities: misalignment of the steering system, one-way flow, different tire friction, etc. (b) Road surface changes: ice burn, μ jump (change in adhesion resistance between the tire and the road surface), etc. (c) Other disturbances: undulations, crosswinds, single gradient, rough road, curb contact, wheel detachment, etc.

[0056] (4) Input the steering reaction force due to the attitude change (Bounce) caused by vertical movement As the vertical movement of the specimen W causes a change in the play angle of the tie rod, a steering change in the reverse phase (toe-in, toe-out) occurs (see Fig. 4). In this case, since there is no steering angle fluctuation and the input enters the steering rack gear W4, the feedback control using the steering angle signal cannot generate the force associated with the steering change in the reverse phase (toe-in, toe-out).

[0057] Therefore, the steering reaction force control unit 33 calculates the steering reaction force generated by the attitude change due to the vertical movement of the specimen W, calculates a command value based on the steering reaction force and the detection signal of the load cell 32, and performs feedback control of the actuator 31 based on the command value. Here, the attitude change Δh caused by the vertical movement of the test specimen W is calculated by the position sensor 7 that detects the height position of the steering rack gear W4. Further, the steering reaction force F generated by the attitude change Δh is calculated by a predetermined arithmetic expression F = f(Δh).

[0058] (5) Input of steering reaction force due to left - right load transfer (roll) during turning The steering reaction force control unit 33 calculates the steering reaction force generated by the attitude change during the turning of the test specimen W, calculates a command value based on the steering reaction force and the detection signal of the load cell 32, and performs feedback control on the actuator 31 based on the command value.

[0059] Here, the steering reaction force is the self - aligning torque affected by the left - right load transfer caused by turning. Specifically, as shown in FIG. 5, the centrifugal force F during turning is F = m×G from the vehicle weight m and the lateral acceleration G lateral and lateral results in Calculate the left - right load transfer Δm generated by this centrifugal force F, and calculate the left - right vehicle heights h Rh +Δh Rh and h Lh +Δh Lh from this calculated Δm. From these left - right vehicle heights, the change in slip angle ΔD Rh and ΔD Lh can be calculated. Then, from the relationships between D Rh -ΔD Rh and m Rh -Δm, the slip angle [deg], and the self - aligning torque [Nm], the self - aligning torque of the right front wheel can be calculated. Also, from the relationships between D Lh -ΔD Lh and m Lh -Δm, the slip angle [deg], and the self - aligning torque [Nm], the self - aligning torque of the left front wheel can be calculated.

[0060] (6) Input of steering reaction force due to attitude change (pitch) during braking or acceleration The steering reaction force control unit 33 calculates the steering reaction force generated by the attitude change of the test specimen W during braking or acceleration, calculates a command value based on the steering reaction force and the detection signal of the load cell 32, and performs feedback control on the actuator 31 based on the command value.

[0061] Here, the steering reaction force is the self-aligning torque affected by the front-rear load transfer caused by braking or acceleration. Specifically, as shown in FIG. 6, for example, the inertial force F during braking is the vehicle weight m and the longitudinal acceleration G long From which F = m × G long It becomes. Calculate the front-rear load transfer Δm caused by this inertial force F, and from the calculated Δm, the front wheel vehicle height h Fr -Δh Fr Calculate. From this front wheel vehicle height, the change ΔD toe Of the slip angle due to toe-in can be calculated. And D Rh +ΔD toe And m Rh +Δm and the relationship between the slip angle [deg] and the self-aligning torque [Nm], the self-aligning torque of the right front wheel can be calculated. Also, D Lh +ΔD toe And m Lh +Δm and the relationship between the slip angle [deg] and the self-aligning torque [Nm], the self-aligning torque of the left front wheel can be calculated.

[0062] (7) Cooperation with the chassis dynamometer 2; Control considering the change in the rolling resistance on the left and right during turning As described in the above "(5) Input of the steering reaction force due to the left and right load transfer (roll) during turning", the rolling resistance received by each wheel from the road surface changes due to the left and right load transfer Δm during turning.

[0063] Therefore, as shown in FIG. 7, the dynamometer control unit 25 calculates the moving load Δm generated during turning, calculates the rolling resistance N (= μm) of the left and right wheels or the front and rear wheels due to the moving load Δm, and based on the rolling resistance N, calculates the load command value for the chassis dynamometer 2 and performs feedback control on the chassis dynamometer 2. In this case, the chassis dynamometer 2 has the front wheel rollers 21 and the dynamometers 23 independently provided for each of the left and right front wheels, and the load command value corresponding to each dynamometer 23 is input. For example, when the load Δm moves from right to left, the rolling resistance F Rh of the right wheel is F Rh = μ(m Rh - Δm), and the rolling resistance R Lh of the left wheel is F Lh = μ(m Lh + Δm).

[0064] (8) Cooperation with the chassis dynamometer 2; Input of the steering reaction force during emergency braking As shown in FIG. 8, when emergency braking occurs during actual running, the anti-lock braking system (ABS) operates and the cornering power (CP) can be generated.

[0065] On the other hand, when emergency braking occurs on the chassis dynamometer 2, since the longitudinal acceleration G long of the vehicle is not generated, the front and rear load transfer Δm does not occur. The running resistance on the chassis dynamometer 2 at this time does not match the running resistance during actual running. Furthermore, the vehicle inertial energy at this time also does not match. Therefore, the deceleration during running on the chassis dynamometer 2 is usually obtained by differentiating the vehicle speed of the vehicle, but during emergency braking, the front wheels W1 of the vehicle are locked and the rollers 21 of the chassis dynamometer 2 are assumed to continue rotating, so the deceleration cannot be calculated and the steering reaction force cannot be obtained.

[0066] Therefore, the steering reaction force control unit 33, during emergency braking of the test specimen W, without using the vehicle speed signal indicating the vehicle speed of the test specimen W, uses the maximum acceleration G calculated from the test specimen specifications (vehicle specifications) maxBased on this, the front-wheel vehicle height change and the steering reaction force are calculated.

[0067] <3. Effects of this Embodiment> According to the vehicle test system 100 of this embodiment configured as described above, by inputting a steering reaction force to the steering rack gear W4 of the specimen W in a state where the steering force of the steering system is not transmitted to the wheel W1 (the state where the tie rod is removed), while the specimen W is running on the chassis dynamometer 2 with the wheel W1 of the specimen W kept in a straight-ahead running state, the steering function of the specimen W can be evaluated. Further, since the steering reaction force input device 3 can input various steering reaction forces to the steering rack gear W4, the steering function under various situations can be evaluated on the chassis dynamometer 2.

[0068] <4. Other Embodiments> For example, the steering reaction force input device 3 of the above embodiment is configured to provide one actuator 31 between the steering rack gear and the tie rod end link respectively, but as shown in FIG. 9, it may be configured using two or more actuators. FIG. 9 shows an example having a first actuator 311 that generates a steering reaction force with a low frequency and a large stroke, and a second actuator 312 that generates a steering reaction force with a high frequency and a small stroke. Here, the first actuator 311 and the second actuator 312 are provided in series between the steering rack gear W4 and the tie rod end link W5.

[0069] Also, as shown in FIG. 10, the first link member 34 or the second link member 35 of the above embodiment may be configured to be replaceable and used as an adjustment attachment that can be adjusted according to the distance between the steering rack gear W4 and the tie rod end link W5. Alternatively, in addition to the first link member 34 and the second link member 35, a configuration may be used in which an attachment that can be adjusted according to the distance between the steering rack gear W4 and the tie rod end link W5 is used.

[0070] Furthermore, although the steering reaction force input device 3 of the above embodiment actively inputs a steering reaction force to the steering rack gear W4, it may be configured to passively input a steering reaction force due to the movement of the steering rack gear W4. In this case, as the steering reaction force input device 3, for example, a passive member such as a spring can be considered.

[0071] In the above embodiment, the steering reaction force input device 3 is configured to be connected to the tie rod end link, but it may be configured to be connected to the steering knuckle, or may be configured not to be connected to the tie rod end link and the steering knuckle. Also, the steering reaction force input device may be fixed to the floor. Furthermore, the steering reaction force input device may be fixed to other parts of the test specimen W.

[0072] Moreover, in the above embodiment, separate actuators 31 are connected to both ends of the steering rack gear W4, but as shown in FIG. 11, a common actuator 31 may be connected to both ends of the steering rack gear W4.

[0073] In addition, as shown in FIGS. 12 and 13, the steering reaction force input device 3 may be configured to input a steering reaction force to the steering rack gear W4 of the test specimen W via the steering wheel W7 or the steering shaft W8. This steering reaction force input device 3 is connected to the steering wheel W7 or the steering shaft W8 and is configured using an actuator 31 as in the above embodiment. Also, when the test specimen has an automatic steering function such as an electric power steering system (EPS), the automatic steering function may not be stopped by the steering intervention determination. Specifically, it is conceivable to modify the control program of the EPS control unit so as not to make a steering intervention determination, to prevent the signal from the torque sensor of the steering system from being input to the EPS control unit, or to input a dummy signal of the torque sensor to the EPS control unit.

[0074] Also, when inputting a steering reaction force via the steering shaft W8, a self-aligning torque can be generated by an actuator 31 that generates a centering force (see FIG. 12). As shown in FIG. 13, the steering reaction force input device 3 may control the steering reaction force by a steering reaction force control unit 11 using a steering angle sensor 8, a reaction force generating motor 9 attached to the steering shaft W8, and a torque sensor 10. Further, instead of using the steering angle sensor 8, the steering angle signal information may be acquired from a vehicle network (for example, CAN).

[0075] In addition, various modifications and combinations of the embodiments may be made without departing from the spirit of the present invention.

Industrial Applicability

[0076] According to the present invention, the steering function of a vehicle having an automatic steering function or a specimen that is a part thereof can be evaluated on a chassis dynamometer.

Claims

1. A vehicle test system for conducting a running test on a specimen that is a vehicle or a part thereof having a steering function, a chassis dynamometer for conducting a running test on the specimen, a steering reaction force input device that is connected between the steering rack gear and the wheels of the specimen with the tie rod connection severed, and inputs a steering reaction force to the steering rack gear of the specimen running on the chassis dynamometer, A vehicle test system comprising: a steering fixation mechanism that enables the wheels to rotate on the chassis dynamometer and fixes the wheels so as not to steer.

2. The steering reaction force input device includes an actuator that generates the steering reaction force, a load cell that detects the steering reaction force applied to the steering rack gear by the actuator, and a steering reaction force control unit that performs feedback control of the actuator using the detection signal of the load cell. The vehicle test system according to claim 1.

3. The steering reaction force input device is connected to the steering rack gear and the tie rod end link via an attachment. The vehicle test system according to claim 1 or 2.

4. The steering reaction force input device has an absorption structure that absorbs relative vertical fluctuations between the steering rack gear and the tie rod end link. The vehicle test system according to claim 3.

5. The steering reaction force input device has a support mechanism that supports its own weight with respect to the floor. The vehicle test system according to claim 3 or 4.

6. The steering reaction force input device inputs the steering reaction force to the steering rack gear of the specimen via a steering wheel or a steering shaft. The vehicle test system according to claim 1 or 2.

7. The steering reaction force input device has an elastic body element that reproduces a dead zone associated with steering. The vehicle test system according to any one of claims 1 to 6.

8. The steering reaction force input device has a first actuator that generates a low-frequency and large-stroke steering reaction force, and a second actuator that generates a high-frequency and small-stroke steering reaction force. The vehicle test system according to any one of claims 1 to 7.

9. The vehicle test system according to any one of claims 1 to 8, wherein the steering reaction force input device includes a release mechanism that releases the steering reaction force applied to the steering rack gear when the steering force applied from the steering of the specimen reaches a predetermined threshold value.

10. The vehicle test system according to any one of claims 1 to 8, further comprising a driving robot that automatically drives the specimen.

11. The steering reaction force control unit calculates a command value for the actuator from a vehicle speed signal indicating the vehicle speed of the specimen or a steering angle signal indicating the steering angle of the specimen, and controls the actuator based on the command value. The vehicle test system according to claim 2 or any one of claims 3 to 10 that cites claim 2.

12. The vehicle test system according to claim 11, wherein the steering reaction force control unit calculates self-aligning torque from the steering angle signal and calculates the command value based on the self-aligning torque.

13. The vehicle test system according to claim 11 or 12, wherein the steering reaction force control unit calculates a command value for the actuator from a vehicle speed signal indicating the vehicle speed of the specimen at low speeds and during parking.

14. The vehicle test system according to any one of claims 11 to 13, wherein the steering reaction force control unit calculates a command value for the actuator based on an abnormality of the specimen, a road surface change, or other disturbances.

15. The vehicle test system according to any one of claims 11 to 14, wherein the steering reaction force control unit calculates a command value for the actuator based on a steering reaction force generated by an up-and-down attitude change of the specimen.

16. The vehicle test system according to any one of claims 11 to 15, wherein the steering reaction force control unit calculates a command value for the actuator based on a steering reaction force generated by an attitude change during turning of the specimen.

17. The dynamometer control unit that controls the chassis dynamometer calculates a moving load generated during turning of the specimen, calculates a rolling resistance of the left and right wheels due to the moving load, and calculates a load command value for the chassis dynamometer based on the rolling resistance. The vehicle test system according to claim 16.

18. The vehicle test system according to any one of claims 11 to 17, wherein the steering reaction force control unit calculates a command value for the actuator based on a steering reaction force generated by a change in the attitude of the test specimen during braking or acceleration of the test specimen.

19. The vehicle test system according to any one of claims 11 to 18, wherein the steering reaction force control unit calculates a command value for the actuator based on a steering reaction force generated by a change in the attitude due to the maximum acceleration calculated from the test specimen specifications without using a vehicle speed signal indicating the vehicle speed of the test specimen during sudden braking of the test specimen.

20. It is for evaluating the steering function of a test specimen which is a driving vehicle or a part thereof on a chassis dynamometer, A steering reaction force input device that is connected between the steering rack gear and the wheels of the test specimen with the tie rod connection cut, and applies a steering reaction force to the steering rack gear of the test specimen based on the steering angle and vehicle speed of the test specimen in a state where the wheels are fixed so as not to steer by a steering fixing mechanism.

21. It is for evaluating the steering function of a test specimen which is a driving vehicle or a part thereof on a chassis dynamometer, The test specimen is run on a chassis dynamometer in a straight-ahead running state by a steering fixing mechanism that fixes the wheels of the test specimen with the tie rod connection cut so as not to steer, A steering function evaluation method for evaluating the steering function of the test specimen by connecting a steering reaction force input device between the steering rack gear and the wheels of the test specimen and inputting a steering reaction force to the steering rack gear of the test specimen.

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