Dynamic plotter

We are looking for a hardware platform suitable for presentation of trajectory optimization algorithms and your goal will be to build one. The platform will resemble a gantry crane or a pendulum on a cart with a variable length if you want. It will be attachable/detachable to a whiteboard and there will be a pen at the place where the hook normally is (or, at the end of the pendulum). The ultimate goal for the platform will be to draw a given curve on the whiteboard in the shortest possible time. Nevertheless, at first, we need you to build the platform for us. When we have the platform, you can also work on the control algorithms. If you like to build stuff this is an ideal project for you as you will have to design, make and assemble all the components (some inspiration can be taken from open-hardware designs of some 3D printers though).