This study presents a unique design for combining an electric motor and its drive circuitry into one integrated package.
Electric motors used in systems such as electric power steering applications commonly consist of a separate electric motor and drive controller. There are several disadvantages to this approach. First, the mounting of two separate items into the system takes extra room and increases assembly complexity. There are several disadvantages associated with the wires that interconnect the two units. The long wires introduce additional electrical resistance. Also, they can act as antennas that both receive and radiate electromagnetic interference.
Mounting a miniaturized motor drive unit directly to the side of the motor achieves some of the advantages of a fully integrated approach but only to a limited extent. Wires still exit the motor and must be attached to the drive unit. Angular position sensors must be mounted to the motor separate from the drive unit. This results in extra electrical connections that add cost and are potential points of failure.
The design presented in this paper places the power drive section of the controller directly on the end of the motor. The digital control board is so placed that sensors for measuring the angular position of the motor can be placed directly on the PCB board. This results in a small package with a minimum number of connections. The viability of this design, from the standpoint of heat transfer, is demonstrated using finite element analysis. Varying parameters in the finite element model identifi the most critical design parameters.
The insights into the nature of mechatronic design gained through this design study are discussed.