Well designing the robot is all very well, but can it walk?  I decided to build a robot simulation using Gazebo, http://gazebosim.org/.   It would have been good to do this earlier in the project as it may have helped with some of the design choices, but the simulation worked well once it was completed.

The gait generation was based on this paper:  https://www.semanticscholar.org/paper/Locomotion-Control-for-Electrically-Powered-Quadru-Ko%C4%8Do/897e209277562b835b8e0e1e07023ac85d05ae12

Though the simulation is far from perfect this bodes well for performance of the physical robot.  I need to clean up the code for the ROS controllers, but I will add the code to the repository soon.

The first tests were to check the actuators worked ok,  it was just moving up and down vertically.

A slow walk, this only lifts one foot at a time whilst the other 3 are moving slowly back. It is looking good.  This is very stable, you can stop the gate at any time and dobot doesn't fall over. It's speed is limited though.

Now a faster trot, this involves lifting two diagonal feet at the same time.   You need to be moving faster for this to be stable, but it also has a higher top speed.