טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentKain Maoz
Subject2nd Generation Development of a Flexible Track Robot -
RoboTrek, for Autonomous Locomotion over High
Obstacles
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Elon Rimon
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

In attempting to robotically locate wounded people beneath the ruins caused by a natural disaster, or map the terrain of tunnels or other urban areas, one tumbles upon a variety of interchanging obstacles from above, below and from its front.

There are several types of robotic platforms that can climb high obstacles, walls and/or staircases. Among these platforms one can find double caterpillar robots that climb low steps and staircases, wall climbing robots using friction, adhesion or vacuum grip, and arm assisted robots or multi-links robots for overcoming high obstacles. All these robots use at least 2 high power actuators and their carrying capacity is very low.

The system proposed in this research is a one high power actuator driven robot which is based on “Four Bar Mechanism”, a configuration of 4 bars connected by 4 revolute joints. This mechanism has one degree of freedom, meaning only one actuator is needed to drive the whole system.

This research demonstrates the development of a smart controlled robot, which will eventually be able to climb steps up to 3 times its height and still crawl in narrow spaces thanks to its 22 cm height.

The robot is made out of aluminum links connected by revolute joints, where each joint can be locked or released for rotation, using a Wrap Spring Clutch mechanism and a servo motor which is controlled by the algorithm of the software commanding it. An Arduino Mega2560 board is used to program the robot’s algorithm and commanding the links actuators, and the wireless RF network.  

The driving mechanism is only one high power actuator which drives the links forward as the joints are released and locked in a synchronized matter. Each link is equipped with sensors such as accelerometers and hall effect in order to receive an input of the relative angle of each of the links and of the relative position to the frame of the robot. 

In the process of this research, alongside the electromechanical design and the testing of a working prototype of the robot, an algorithm was developed, analytical static simulations of climbing were tested, in order to sharpen the algorithm, and a formula was formulated, describing the relation between the number of links that is needed, in order to climb a step in a desired height, with a given link length and height.

The current prototype of the robot had succeeded in climbing a 30 cm step with 26 links with a link length of 65 mm and height of 47mm. Furthermore, the prototype had succeeded in overcoming a staircase. The highest speed tested for a plane crawl was .

Preliminary tests of another configuration with 30 links and a step height of 40 cm. From these few experiments, it can be concluded that the main problems of overcoming a step this high is a combination of the suitability of the algorithm to each height of the step and the inconsistency of the locking mechanisms’ holding torque.