This research has designed a new hybrid-electric system, which is characterized by two mechanisms: internal-combustion engine energy-distribution mechanism and dual energy-integration mechanism. The internal-combustion engine energy-distribution mechanism comprises a first pulley-set and a second pulley-set, whereby it is possible to adjust its radius ratio and change the output load according to the road-surface, output speed and corresponding load to maintain an optimal operating state of engine for a given generator rotational-speed. In this way, the engine can function in its optimal state. For a dual energy-integration mechanism, any power source can be individually actuated by the electric motor and the power transmitted from the internal-combustion engine energy-distribution mechanism. Moreover, a one-way clutch can prevent the actuated power source from reversion, so any output power source will not be affected by any inactive power. Also, two input power-sources can be integrated into a bigger power source via the dual energy-integration mechanism, thus resulting in twice the output energy and obtaining the necessary tractive power. A dynamic equation is therefore derived from this system to obtain the flow direction for the power source. Furthermore, dynamic equations of various system components can be established by the modularized software Matlab/simulink, and fuzzy logic is used to control and develop this system's dual energy-integration mechanism as a control strategy. It can be learnt from the system simulation that, after the engine's energy is distributed by the controller of the dual energy-integration mechanism, subjected to a deceleration ratio of the first pulley-set of the internal-combustion engine distribution mechanism and added to the generator torque transmitted from the second pulley-set, the engine can maintain an optimum state under various operating conditions. (C) 2004 Elsevier Ltd. All rights reserved.