An electric power steering system (EPS) has been developed for an all-terrain vehicle (ATV), based on an automobile EPS system. The new EPS has been employed in the 2007 TRX500FPE FourTrax Foreman 4X4 ES. The EPS unit has been made compact to enable fitting without having to modify the vehicle configuration. Optimization of the size of the motor, the reduction ratio, and the spring rate of the torsion bar has enabled the prior ATV steering torque to be halved in both 2WD and 4WD operation, and has resulted in the achievement of a balance between reduced kickback and the maintenance of an appropriate level of feedback from the road surface. The use of a configuration that enables the EPS unit to avoid external loads (use of bearing holders, etc.) and a waterproof structure has helped ensure that the unit satisfies the requirements of ATV use.
Article of Honda R&D Technical Review Vol.19 No.2 (45 - 49)