If you ever made an autonomous robot, differential or holonomic, you’ll have experienced that they most often don’t move very elegant. Agilis, my current robot didn’t move smoothly either. This is because it’s movements are composed of different actions. Each action, driving, turning and all the other fancy movements it can make, is very smooth by itself as you could see in previous video. But, when going from one action to the other, the robot experiences violent changes in wheel speed. This leads to wheel spin, sliding and large errors in positioning. The robot tries to go from one speed (one action) to a different speed (second action) in a moment.

One way to solve this problem, is to make the robot accelerate and decelerate at the beginning and ending of each action. This will get rid of the positioning errors and violent accelerations. But it will mean that there is a stop between each action, and that is not what I want for a fast moving robot like Agilis.

The way I made Agilis move smoothly is by action blending (as I call it). By this I mean that I let an action fade out while the next one fades in. Just like a DJ mixes tracks or a painter mixes colors. This works very well as you can see in this video. We see Agilis cutting corners when instructed to drive a square. The cutting of a corner is the result of blending in two actions, one saying, go forward , the other saying, go left. The blending also depends on the speed of the robot, a faster moving robot needs a bigger corner to turn. But also on it’s capability to brake and accelerate. The quicker it can do this, the smaller the turns it can make. I fiddled with this in the video.

There were a lot of technical and logical considerations when implementing action blending in code. I think most of you can’t be bothered by this, so I won’t discuss them unless there proves to e a demand for this. To facilitate further developments and overcome errors if needed I made action blending optional in my code.

Two things bother me. One is that with short actions or low values for acceleration more than two actions can overlap in time. I can only handle two. The other is that I haven’t got angle (between two actions) in the equation, so the results are angle specific. Giving good results with square angles only.

I have been using Premiere Elements 11 for the last two video’s and obviously still need to learn a lot. Sorry for the vague green texts, I don’t know how to fix that. They were perfectly sharp when I wrote them on the floor.