Design & Development of A High Torque Electrical Actuator & its Control Mechanism

Abstract

This project embodies the work done to design and develop an electric actuator having a high power density and high efficiency. Electric actuators, as opposed to their hydraulic counterparts, eliminate the prob- lem of poisonous gases, are easier to maintain owing to elimination of hydraulic leaks and have better diagnosable ability. The added advantages are reduced weight and complexity of power transmission paths, better energy efficiency and better actua- tor dynamics. There are several forms of electrical actuators, mainly classified as linear and rotary electrical motors. In this project, the latter type of electrical actu- ators has been taken up as the subject of research. A thorough theoretical study has been carried out of the various configurations of electric motors available In order to down-select an electric actuator satisfying all above needs and constraints. Electric motors are categorized into Radial Flux motors and Axial Flux motors. The literature survey says that among the radial flux machines, the permanent mag- net motors viz., Permanent Magnet Brushless D.C. motor (PM BLDC), Permanent Magnet Synchronous Motor (PMSM) offer higher power density and efficiency as com- pared to an Induction motor of the same frame size. The design and Finite Element Analysis of the above radial flux machines, using SPEED Software is done in this project. SPEED (Scottish Power Electronics and Electric Drives) is a consortium of industries with common interest in Power Electronics and Electric Drives. It is found that the surface mounted PM BLDC motor offers the highest power density and efficiency among the radial flux motors. The surface mounted PMSM motor, comes a close second. The PMBLDC motor is preferable to the PMSM motor owing to relatively simple trapezoidal control. Among the several available topologies of axial flux permanent magnet motors, it is found that the Segmented Armature Torus Topology suits the project require- ments on the theoretical front. A detailed analysis of SAT AFPM is carried out in this project, and its Finite element analysis carried out for different pole and stator vi slot combinations. This has been done using MagNet 6.27 SP1. It is found that the SAT topology AFPM motor is superior as compared to the radial flux machines and other AFPM motors in its frame size, in terms of power density and efficiency. The added advantages are, compact construction, better cooling facility, and adjustable air gaps, better utilization of field developed by the permanent magnets. Different controller topologies for the AFPM motor are also included in the project.