Abstract
Purpose of the diploma thesis was to find out methods to analyse the effect of the different tyre variation on lateral handling. To gain repeatable results and increasing the quality of measurement objective methods was used.
The tests and signal processing were done according to the standards: two closed loop tests constant radius (ISO 4138) and obstacle avoidance (ISO 3888-2) and one open loop test step steer (ISO 7401). The test vehicle was equipped with motion pack (DGPS, gyro and accelerometers), steering robot, combined brake and accelerator robot. The robots were programmed so that the test vehicle performed manoeuvres according to the test requirements. The test area was large dry tarmac track. Two sets of tyres with minor differences were used.
For evaluating constant radius test self-steering gradient, vehicle sideslip angle gradient, and characteristic velocity parameters were established. For analysing obstacle avoidance vehicle’s axle position were calculated, quadratic cost of steering work and route deviation. The step steer response was evaluated by lateral acceleration and yaw velocity response times, over shoot value of yaw velocity and lateral acceleration, and steady-state yaw velocity response gain. Signals were filtered with 5 Hz low-pass Butterworth filter. Each measurement was repeated three times. The measured data was averaged or curve fitting tool was used. For each curve error limits were announced. Chosen methods were able to point out minor differences between tested tyres.
This thesis applied ISO-standards which are normally used subjective testing to robot controlled vehicle testing.
Constant radius test describes vehicle handling, step steer test shows the agility of the vehicle and obstacle avoidance tells the safety of the vehicle. Comparing test results with different tyre sets it was able to determine differences. Chosen test methods and signal processing gives a solid step stone for analysing tyres.
KEYWORDS – Lateral handling, objective handling evaluation, obstacle avoidance, step steer, constant radius