Or you can use your Nano and my Arduino Library for Meccano MAX which uses bit-banging instead of a com port to control MAX's face. The com port can then be used for the serial monitor. 
And if you have time, have a look to see how to consistently get the IR sensor to report the distance (value returned by sensor and the distance is not a linear function but we can work it out). And also if there are commands to change the speed of the motors or keep the motors running without having to periodically send them a command.
Getting home sick?