Startup interlock for vehicle electric drive system

In vehicle electric drive systems having an internal combustion engine, an electric generator driven by the engine, a first inverter/rectifier coupled to the generator, a buss coupled to the first inverter/rectifier, a second inverter/rectifier coupled to the buss, and a traction motor coupled to an output of the second inverter/rectifier and driving a wheel, an operator speed command lever movable from a zero speed position to a high speed position, an operator speed command pedal movable from a zero speed position to a high speed position, an operator direction control member having forward, neutral and reverse positions, and a controller coupled to the second inverter/rectifier for controlling a current output of the second inverter/rectifier as a function of positions of the speed command lever, the speed command pedal and the direction control member, a startup interlock method:

• upon startup, sensing position of the direction control member, sensing wheel speed, sensing position of the speed command lever, and sensing position of the speed command pedal;
• preventing vehicle operation if the direction control member is not in its neutral position, or the sensed wheel speed is not close to zero, or the speed command lever is not near its zero speed position, or the speed command pedal is not near its zero speed position;
• and
• permitting vehicle operation if the direction control member is in its neutral position, and the sensed wheel speed is close to zero, and the speed command lever is near its zero speed position, and the speed command pedal is near its zero speed position.