Switch-Mode Continuously Variable Transmission Prototype Design and Testing

2009 ◽  
Author(s):  
Jeffrey Araujo ◽  
Michael DeMalia ◽  
Christopher Lambusta ◽  
Anthony Morocco ◽  
James Van de Ven
Keyword(s):  
Continuously Variable Transmission ◽  
Switch Mode ◽  
Variable Transmission ◽  
Design And Testing ◽  
Prototype Design

Switch-Mode Continuously Variable Transmission: Modeling and Optimization

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
James D. Van de Ven ◽  
Michael A. Demetriou
Keyword(s):  
State Space ◽  
Damping Ratio ◽  
High Energy ◽  
Continuously Variable Transmission ◽  
Drive Train ◽  
System Stability ◽  
High Energy Density ◽  
Duty Ratio ◽  
Switch Mode ◽  
Variable Transmission

Hybrid vehicles are an important step toward reducing global petroleum consumption and greenhouse gas emissions. Flywheel energy storage in a hybrid vehicle combines high energy density and high power density, yet requires a highly efficient continuously variable transmission with a wide operating range. This paper presents a novel solution to coupling a high-speed flywheel to the drive train of a vehicle, the switch-mode continuously variable transmission (CVT). The switch-mode CVT, the mechanical analog of a boost converter from power electronics, utilizes a rapidly switching clutch to transmit energy from a flywheel to a spring, which applies a torque to the drive train. By varying the duty ratio of the clutch, the average output torque is controlled. This paper examines the feasibility of this concept by formulating a mathematical model of the switch-mode CVT, which is then placed in state-space form. The state-space formulation is leveraged to analyze the system stability and perform simple optimization of the switch time and damping rate of the spring over the first switching period. The results of this work are that a stable equilibrium does exist when the speed of the output shaft is zero, but the system will not reach and stay at a desired torque if this condition is not met, but requires continuous switching between the two states. An optimal switching time and damping ratio were found for the given parameters, where the lowest error occurred with low values of damping ratio. This work builds a foundation for future work in increasing the complexity of the model and the optimization method.

Switch-Mode Continuously Variable Transmission With Flywheel Energy Storage

2008 ◽  
Author(s):  
Tyler D. Forbes ◽  
James D. Van de Ven
Keyword(s):  
High Speed ◽  
Continuously Variable Transmission ◽  
Drive Train ◽  
Mechanical Transmission ◽  
Ground Vehicles ◽  
Power Sources ◽  
Output Torque ◽  
Switch Mode ◽  
Variable Transmission ◽  
Energy And Power Density

A hybrid drive train significantly improves energy efficiency of ground vehicles. While numerous auxiliary hybrid power sources have been researched, few are capable of the energy and power density of a flywheel coupled with a continuously variable mechanical transmission. The primary challenge of a flywheel hybrid system is a transmission capable of coupling a high speed flywheel to the drive train of the vehicle. A novel solution to this challenge is a switch-mode continuously variable transmission that utilizes a rapidly switching clutch to transmit power. This system, the mechanical analog of a DC-DC boost converter circuit, utilizes a flywheel, a high frequency clutch, an anti-reversing ratchet, and a spring to vary the output torque. The switch-mode continuously variable transmission is demonstrated through an idealized finite difference model, created from the dynamic system of equations. The model is used to demonstrate the system behavior in a passenger car subjected to road loads in various conditions. The output of the model demonstrates pulses in the output torque as a result of the rapidly switching clutch. This output ripple in is smoothed to an acceptable level by the torsion spring. From this preliminary analysis the on-off continuously variable transmission offers an efficient, energy dense, and power dense hybrid vehicle drive train alternative.

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