Decision-making of the theme by students in a case study and its results

We have had a curriculum called "Case Study on Design of Mechatronics Systems" and various robots were made by the students. One of the most important and difficult factors to make the case study success is how to decide its theme. In the first four year's practices, faculties decided the themes. In these practices, there were some students who weren't interested in and didn't do their best in the fifth practice; the theme, "Ensemble Robot", was proposed by the faculties and was decided by the discussions of the students. To decide the theme by the students' discussion had some good points. So, in the sixth practice, the theme was entirely decided by the students. The features of their discussion was that they intended to make robots which audiences could be amused by seeing them at our cultural festival. They were also interested in the robots related to Japanese culture. The resultant theme was "Horseback Archery Robot". Although the decision-making took a long time, once it was decided, the students did their best and made some interesting robots including various mechanisms. Although there were some groups who couldn't complete their robots, all the students felt satisfaction. In this paper, how the decision-making was done and how the interesting mechanisms were made are reported.