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This paper concerns a torque control of a rear wheel of a motorcycle equipped with a rubber/aramid belt electronically-controlled continuous variable transmission where a primary sheave position is controlled by an electric motor. In particular, the paper discusses a method to calculate a required engine torque and a required primary sheave position, given reference values of a rear-wheel torque and an engine rotational velocity. The method forms a foundation of a hierarchized traction control where a higher control layer decides an optimal motorcycle motion (rear-wheel torque and engine rotational velocity) and a lower control layer realizes the motion by actuators (engine torque and primary sheave position). Difficulties of the control are due to large mechanical compliance of the rubber/aramid belt, which leads to an inevitable lag from the primary sheave position to a speed reduction ratio.

Today, environmental issues have become major global issues. Under these social circumstances, restrictions on vehicles powered by internal-combustion engines have become increasingly stringent. While, many models of motorcycle are intended for hobbyists, and enjoyment is a major factor in the appeal of these products. So it is necessary to simultaneously realize improved environmental performance and heightened enjoyment. Therefore, the authors focused on controlling the richness of the mixture, the air-fuel ratio. In the case of intake port-injection engines, it is common these days to control fuel injection using a fuel model that takes fuel adhered in the intake port into consideration, in order to control the air-fuel ratio. When this method of control is used, it is necessary to derive the ratio of injected fuel that adheres inside the intake pipe and the ratio of adhered fuel that is drawn into the cylinder.