Controlling a one-link robot in a real-time manner is not difficult, but on the other hand it is not a trivial task. This is the basis of controlling multi-link manipulators, and it gives an indication of the type of problems and difficulties that arise in a larger environment. The idea is to establish a complete model for controlling and simulating a one-link robot, starting from the analysis and design, through the simulation and error analysis.
A motor from the Mechanical Engineering lab was used. This motor is controlled by a PID controller. An analog I/O card, named PC-30D, connected to a Hewlett Packard PC was used to connect the motor with the serial port of the PC. This card has sixteen 12-bit A/D input channels, two 12-bit D/A output channels. There are also the card interface drivers with a Quick BASIC program that uses the card drivers to control the DC motor.
One of the problems we faced in this process was to establish the transfer function between the torque and the voltage. The motor parameters were used to form this function by making some simplifications, since some of the motor parameters have nonlinear components that make it too difficult to make an exact model. Figure 17 shows the relation between torque and voltage for a certain input sequence, and Figure 18 shows the circuit diagram of the motor and its parameters.
Figure 17: The relation between torque the voltage.
Figure 18: Circuit diagram of the DC-motor used in the experiment
In general, this experiment gave us an indication of the feasibility of our project, and good practical insight. It also helped us determine some of the technical problems that we might face in building and controlling the three-link robot. More details about this experiment can be found in [9, 49].