Control system for Robo-Team's Micro Probot
By Amir Arbel & Udi Feintuch
The use of robotics in warfare is becoming increasingly significant among various security forces throughout the world. The primary goal of integrating robots into combat situations is the saving of human lives. The possibility of using robots for complex missions can greatly reduce the danger to soldiers in the field. The micro-probot , one of the most advanced robots of its kind, is currently in the development stages at the Robo-team company. The company was founded in 2009 and does development and integration of defense products which are adapted to the needs of the buyer. The robot's uniqueness lies in its high level maneuverability, and its relatively small size and weight. The robot is moved in space by means of an advanced system of treads, and while travelling on a level surface its fixed parts come in contact with the ground. When it is necessary for the robot to pass over obstacles it activates a system of flippers thus increasing the contact area of the treads. In addition the flippers propel the robot over the obstacle, thus allowing superior maneuverability.
The purpose of our project is to design a control system for the robot which will allow it some semblance of independence in the field. Since the robot must perform in varying field conditions it must be capable of reacting to the changes in the conditions, while preserving its designated travel route. For example, while ascending a steep incline, if one of the motors doesn’t compensate for the sharp gradient, the robot will deviate from its designated path. The first stage of our project describes the technical design by which we will develop the appropriate control system. Panoramic cameras and a Safire camera provide precise visual feedback in order to improve the control performance. A Tablet user interface was chosen to facilitate the use of a microprocessor . Joysticks were selected to guide the micro manually. All these sophisticated systems are controlled by micro-controllers using a cortex core designed by the Gumstix corporation. In addition, the optimal motors were chosen to propel the robot and activate the servoflipers.
The report describes in detail a kinematic model which allows us to identify at any given point in time both the location of the micro and its orientation in space. In the kinematic modeling the main difficulty is dealing with slippage and therefore there is detailed attention to this issue. The next section deals with the development of the control system of the micro. We chose a PID controller , designed a block diagram , and wrote code in C which implements the design. In addition we researched different methods for computing the constants of the controller and in the end chose the Zeigler-Nichols method. In the research that we carried out as part of this project we saw that it was necessary to test the performance of the robot vis a vis the requirements of the buyer (the U.S. Army) , under conditions similar to those used in testing other such robots. For this purpose we designed an obstacle course which simulates as much as possible the challenges the robot will have to confront in the future. In addition these tests will allow us to check the performance of the robot after integrating the various control systems which we designed.
figure 1: The Micro-Probot