Development Of Double Roller Type Test Bench For Flexible Chassis

The flexible chassis(FC)is a four wheel independent drive and a four wheel independent steer power chassis based on the Off-centered steering axis.By using a generation of prototype,the second-generation prototype of the FC was developed.To detect the motion and the dynamic performance of the second-generation prototype of the FC,a double roller test bench for the FC was designed and manufactured.The test bench consists of 4 pairs of rollers,4 horizontal rotating platforms and a frame,and the horizontal rotating platform that is arranged under each driving wheel of the test chassis and is concentric to the steering shaft of the drive wheel.The rotating range of the horizontal rotating platform should be greater than the rotating range of the test drive chassis rotary shaft in order to locate the test target.A pair of double roller rotating mechanisms was fixed to the horizontal axis on the horizontal rotary platform.A pair of meshing bevel gears was mounted under each rotational central axis.The four large bevel gears were kept at the same rotational speed by the sprocket connection in the front-rear direction and by the bevel gears in the left and right direction.The small bevel gear was connected to the horizontal rotary platform through a horizontal axis.The small bevel gear is able to rotate on its axis,while simultaneously revolving around the large bevel gear.This is possible because the differential drives the horizontal rotation platform rotation.When the four drive wheels of the flexible chassis rotate at the same speed,since the driving wheel is in close contact with the double rollers,the rollers can be rotated by the driving wheel,where the data of the straight-line test can then be collected.When one chassis drive wheel speed is different from the other three drive wheel speeds,The reference of the differential rotation occurred when the rotation of the bevel gear that is mounted on its center of rotation was not equal to the rotation speed of the other three identical rotation center axes,where the data of the FC steering test could be carried out.A theoretical and technical reference is provided for the further development of FC and its controller.The main contents and achievements of the paper are as follows:(1)Combined with the design of the first generation test bench and the principle of the automotive chassis dynamiter,a double roller test bench which takes the planetary gear system as the main body,speed difference as the steering mechanism,and drive wheels as the power source for the FC was designed and manufactured.(2)The control system of the test bench was designed.The control system completes signal acquisition,communication,speed control,current monitoring,and data saving.The main test bed detection signals are the speed of the four-wheel motor of the FC,the rotation speed of the roller on rotary platform,the input current of each wheel motor,and the value of the four force sensors.These works ensure the accuracy and timeliness of the test data.(3)The simulation test requires the use of the FC wheel motor drive electric wheel movement,which drives the double rollers rotation for the double rollers chassis test bench,and the test results are compared with those obtained by ADAMS software simulation.(4)In the simulation test,the FC can use straight steering and transverse steering.Even in different speed conditions and posture the speed that the FC wheel hub motor increases from 0 to the set speed(about 2-3 seconds).The rotational speed of the FC wheel hub motor was greater than the rotational speed of the driven rotors at 5-10 rpm.At a set speed of 50r/min,the traction of the FC is subjected to 3402 N in straight steering,and the traction of the FC is subjected to 3634 N in transverse steering,then the error between simulation results and test results is less than 15%.The chassis produced a counterclockwise moment,which indicated that the driving force of the right hub motor was greater than the driving force of the left hub motor.This was caused by the resistance error of each double roll mechanism during the manufacturing process and the performance error of each hub motor and the system structure error.Therefore,a control strategy needs to be developed for use during the actual operating state,since the chassis will likely encounter this problem during road and field travel where the degree of difference will be greater.Therefore,the FC control system will require constant monitoring and adjustment.