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The full and half toroidal CVT have been the subject for many research papers. The efficiency and behavior in steady state of both topologies has already been discussed in detail but until now no special attention has been given to their behavior during ratio variation. Therefore, this paper discusses the comparison of the full and half toroidal CVT during periods of ratio variation focusing on the dynamic response and efficiency. The geometrical constraints for the comparison are as follows: equal output inertia, equal maximum output torque at a speed ratio of 1 and identical radial size. The results of the study are based on a model that describes the behavior of both topologies and an algorithm that determines the optimal ratio variation. The outcome of the study shows that the half toroidal outperforms the full toroidal CVT over the entire operating range in terms of dynamics and efficiency during ratio variation. [ABSTRACT FROM AUTHOR]

This paper investigates the trade-off between efficiency and dynamics of CVT's. Energy efficiently varying the speed ratio of the CVT while maintaining the dynamic requirements is of primordial importance to fully utilize the advantages of the CVT in a drivetrain. Although the toroidal CVT is thoroughly discussed in literature, few articles describe its behavior during ratio variation. Therefore, in this paper a procedure is proposed to achieve optimal ratio variation in terms of settling time and efficiency with a half toroidal CVT. The key concept on which the procedure is based is the expression of the maximum output torque of the CVT. It turns out that the given method offers the fastest possible speed ratio variation for given constraints without excessive increase in slip and thus limited loss in efficiency. The most important constraint proves to be the clamping force which has a profound impact on the resulting dynamics and efficiency of the CVT. The paper indicates that higher clamping forces increase the dynamics of the CVT at a certain cost of loss in efficiency which implies that there is a trade-off between efficiency and dynamics. [ABSTRACT FROM AUTHOR]

• Derivation of power loss scaling laws for planetary reducers. • Fast and accurate generation of efficiency maps of scaled reducers. • High-speed testing of planetary reducers at speed values up to 14,000 rpm. • Experimental characterization of both load-independent and load-dependent losses. • Data-driven modeling of the power loss of planetary reducers. Scaling laws are increasingly recognized as an interesting solution to accelerate the early stages of the development of drivetrains. Concerning gearboxes, prior studies focused on geometric scaling to achieve new desired torque and speed values and to predict mass, volume, and inertia. Power loss scaling laws are still lacking in literature. This paper seeks to bridge this gap by proposing scaling laws for the power loss of high-speed planetary reducers. Due to the lack of reliable information on the losses at high-speed, scaling laws are derived from an experimental campaign of 5 commercial planetary speed reducers. The proposed scaling laws are defined based on high-level specifications of the drivetrain, namely the maximal input speed, output torque, and gear ratio. The results suggest that the derived scaling laws can predict the efficiency and power losses with an average error of less than 1%, and 8% respectively relative to the measurements, considering a torque scaling factor of up to 4, speed scaling factor of up to 0.6 and gear ratio scaling factor of up to 2. [ABSTRACT FROM AUTHOR]

In most applications where a variable transmission is required, either an EVT or a CVT would be viable options. In order to obtain a justified decision between both variable transmissions, the operating range and efficiency should be known better. To be able to pinpoint the pros and cons based on efficiency and operating range, a detailed comparison is necessary. However, to the knowledge of the authors there is no such study reported in literature so far. In this paper a permanent magnet Electrical Variable Transmission (EVT) is benchmarked against a half toroidal Continuously Variable Transmission (CVT) and this during steady state conditions. This paper provides the constraints for the comparison and results based on detailed models of both technologies. Two comparative studies are carried out: on one hand a study based on equal maximum output torque and on the other hand a study based on equal rated power. The outcome of the study shows that the CVT is in favor for high input torques and that the EVT is dominant for high input speeds. [ABSTRACT FROM AUTHOR]