Simulation Techniques for Determining Motorcycle Controllability Class according to ISO 26262 2018-32-0060
The ISO 26262 standard specifies the requirement for functional safety of electrical and electronic systems within road vehicles. We have accumulated case studies based on actual riding tests by subjective judgment of expert riders to define a method for determining the controllability class (C class). However, the wide variety of practical traffic environments and vehicle behaviors in case of malfunction make it difficult to evaluate all C classes in actual running tests. Furthermore, under some conditions, actual riding tests may cause unacceptable risks to test riders. In Part 12 Annex C of ISO/DIS 26262, simulation is cited as an example of a technique for comprehensive evaluations by the Controllability Classification Panel.
This study investigated the usefulness of mathematical simulations for evaluating the C class of a motorcycle reproducing a malfunction in either the front or rear brakes. To estimate the rate of rate of successful harm avoidance in this scenario, which is considered useful in judging the C class, we calculated whether a representative rider can stop while leaving a safe distance to a hazardous object. For the calculations, we used time-series waveforms of the brake actuation force described by parameters such as the brake reaction time and the maximum brake actuation force. These parameters were chosen from the data that riders’ compensatory control actions were recorded during the actual riding tests. The rates of successful harm avoidance obtained from the calculations showed the almost same tendency as the results of the actual riding tests. This agreement indicated the rate of successful harm avoidance can be estimated with simulations that use brake operation waveforms to model the compensatory control action.