In this paper, a macroslip detection method is proposed for a metal V-belt continuously variable transmission, and a clamping force control strategy is suggested on the basis of a macroslip detection method. Using the rotational accelerations of the primary and secondary pulleys, the velocity of the secondary pulley and the speed ratio of the continuously variable transmission variator, observation signals are defined. The characteristics of the observation signals are investigated by simulations in a vehicle-driving environment. It is found that two observation signals became unsynchronized when macroslip occurs. Considering the oscillations of the acceleration signal and the noise from the sensors or the differentiating process, a signal-processing method for the observation signals is suggested. Based on the signal-processing results, a variable called the ‘amplitude difference rate’ is introduced for slip evaluation. A macroslip detection method that uses the amplitude difference rate is proposed. The effectiveness of the macroslip detection method is validated by experiments. It is found from the experiments that the proposed method can effectively detect macroslip with an acceptable time delay. In addition, a clamping force control strategy based on the macroslip detection method is developed. In this strategy, the clamping force is maintained at a minimum value with a safety factor of 1 in normal driving conditions but an additional clamping force is applied when macroslip is detected. It is found from the simulation results that macroslip is eliminated by clamping force control. It is expected that the efficiency of the continuously variable transmission system can be improved by reducing the marginal clamping force using the proposed macroslip detection method and the clamping force control strategy.

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In this paper, an energy management strategy with a real time feature is proposed for a CVT (continuously variable transmission) based parallel hybrid electric vehicle. The purpose of this study is to avoid using the engine to charge the battery directly, which provides improved energy efficiency. For this purpose, the recuperated energy during the regenerative braking is distributed in a geometric series way to the on-coming discharging processes which has a dynamic converging characteristic. A simulator is developed by the co-simulation of Cruise and MA TLAB/Simulink. Performance of the proposed strategy is investigated by comparing with that of a rule-based control strategy. It is found from the simulation results that improved fuel economy is achieved and battery SOC (state of charge) is well maintained.I.

In this study, a macroslip detection method is proposed for a metal V-belt continuously variable transmission. The macroslip detection method was developed using the instantaneous periods of the primary pulley's acceleration and the secondary pulley's acceleration, which can be obtained from the existing speed sensors. To obtain the instantaneous periods of the accelerations of the pulleys in real time, a signal-processing method was developed on the basis of zerocross detection. Using the instantaneous periods, the period difference is introduced, and a threshold value b is defined to evaluate the slip state. The characteristics of the period difference and b were investigated by a three-dimensional analysis, in which a three-dimensional model of the continuously variable transmission including the blocks, the bands and the pulleys was constructed, and the velocity of each element and the slip rate were obtained. From the simulation results, it was found that the period difference stays below the threshold value b in the microslip region and begins to increase over the threshold value b in the macroslip region. The macroslip detection method proposed in this study was validated by experiments, which showed that the method is effective for detecting the occurrence of macroslip, independently of the input torque and the speed ratio.

In this paper, a 2 stage continuously variable transmission (CVT) shift control algorithm is proposed for the 1–2 upshift of the planetary gear to achieve the shift quality. A fuzzy control algorithm is designed considering the relatively slower response characteristics of CVT. In order to evaluate the performance of the control algorithm, a 2 stage CVT vehicle simulator is developed including a dynamic model of the CVT powertrain. From the simulation results, it is found that CVT gear ratio changes faster in the inertia phase and remains constant after the inertia phase of the planetary gear shift, which provides the reduced torque variation by the proposed control algorithm.