Abstract
This paper describes a speed-ratio control system of a half-toroidal CVT by measuring only rotational speeds instead of mechanical positions of offset and attitude angle of a power roller. The control system replaces the attitude angle with the speed ratio, and the offset with the differentiation of the speed ratio according to the modeling of the speed-ratio changing mechanism. The control quality is confirmed experimentally by using a double cavity half-toroidal CVT a speed-ratio of 1:5.2 and input torque capacity of 370Nm.