Experimental study of hybrid cam mechanism

Abstract

In this paper we have presented a programmable hybrid mechanism (PHM) capable of producing various types of translatory profiles while carrying loads of up to 5 kilograms. The output is driven by a five bar mechanism, which, in turn, is driven by a servo input and a reference input. By choosing the correct trajectories of the servo input and the starting position, the torque sharing characteristics can be improved, such that the lowest rating servo motor will suffice. Thus providing flexibility at a reduced cost. Also the reference input which can be a constant speed motion can be derived from some other source, thus not needing a dedicated motor. Such a device can replace cams in applications where the functional relationship between the input and the output motions changes from time to time, such as packaging equipment and control of valve timings of IC engines. The PHM setup has been designed and fabricated. Simulation of the mechanism is carried out using ADAMS, to determine the size of servo motor. An approach to determine optimal control input to the mechanism for a given output profile is discussed. The experimental setup allows users to generate various cam profiles and study the deviations. Various profiles were generated within reasonable accuracy. A typical cam profile has been considered and optimization of control trajectory results in RMS torque reduction of 57%.