A method for optimising the weight and response of brush-type wound-field direct current motors

Weight optimised direct current (DC) motors have been used lately as actuators for micro-robotics and biomedical equipment. The evolution of these motors originated from the need for lightweight compact motors with good response in the industry. Many techniques have been used in developing permanent magnet (PM) and wound-field (WF) DC motors, such as numerical analysis, selecting adequate magnetic material, finite element analysis and optimisation models. Yet, published articles on optimising the weight and response of WF DC motors reveal the development of WF weight optimised motors with problems for example non-proportional geometry, saturated armature teeth, weak output torque and high operating specific electric loading. To overcome these problems, this paper presents a method that separately optimises wound-field DC motors operating with closed-loop proportional, integral and derivative (PID) controllers. A 900-watts DC motor and its PID controllers are optimised as an example for illustrating the proposed method.