Try declaring it as
Code:
RobotDrive *myRobot = new RobotDrive( 1, 2, 3, 4 );
// this creates a pointer to the object's memory location
or
Code:
RobotDrive myRobot( 1, 2, 3, 4 );
If you use the first one and it works, whenever you use any of the object's member functions, you will have to type
Code:
myRobot->TankDrive( /* arguments */ );
as opposed to
Code:
myRobot.TankDrive( /* arguments */ );
which will work for the second version