A primary controller disclosed. The primary controller is configured for controlling operation of a drive system comprising a prime mover, a generator, and a motor, wherein the prime mover is configured to provide energy to the generator, which is configured to drive the motor. The controller comprises a speed controller configured for determining a target speed of the motor dependent on externally-supplied speed input and a torque controller configured for determining a target torque of the motor based on externally-supplied torque input and on parameters of the vehicle. The primary controller is configured to simultaneously determine the target speed and the target torque and to simultaneously control the prime mover, generator, and motor to operate the motor at the target speed and the target torque.