Control System and Method for Transport Device

A selectively powered transport device such as an ambulatory stretcher-chair is presented. The stretcher-chair has a spring-biased Hall-effect mechanism controlled by an operator to command a desired direction and speed of mobility of the device. A power drive control unit senses a target direction and speed of movement and incrementally closes on that target. The power drive control unit senses the presence of ramps or inclines by monitoring instantaneous current to a drive motor and adjusts the motor operation accordingly. The power drive control unit further monitors thermal operational conditions of the drive motor by monitoring motor winding current and assessing energy dissipated as heat in the motor winding as a function thereof. The net accumulated heat energy associated with the motor is monitored and corrective action with respect to the current applied to the motor is taken accordingly.