Shaojie Ge

Special Sensor System  My special sensor system is the walk mechanism of my robot. Since my robot is a walking robot with four legs. It is important to make the robot walk straight stably with these legs without falling down.

Special Sensor System  The main issue of designing the walking mechanism is to set correct parameters on each servo motor to control its position and movement speed in every walking step of the robot.  The purpose is to make every joint is compatible with other joints so that they will not interrupt each other, thus move the robot forward instead of staying at the same place or slipping around.

Connection  SSC-32 Hardware Information  The image shows the shorting bar jumpers of the SSC32 servo driver board. For my project, I choose to power both the power terminal VS1, VS2 and VL with a 6V NIMH battery pack. Thus I keep 3, 5 connected.

Connection  I connected the servo motors on the same side to channel 0 to 3, and the servo motors on the other side of robot to channel 16 to 19.  The SSC32 and Arduino mega 2560 is connected by a wire between the serial port TX0 on Arduino and port RX on SSC32.

Servo movement control  The control of the servo motors is done with Arduino develop tool. To make a servo move at a desired speed to a desired position, I need to send a control code via the serial port to the SSC32 by Arduino.  An example: “#5 P1600 #10 P750 T2500 ”, this will move servo #5 to position 1600 and servo #10 to position 750. The entire movement will take 2.5 seconds.

Servo movement control  The motion of walking can be divided into 8 portions. Basically it is a alternating waking mechanism. When the front-left and rear-right legs are upshifting to push the robot advance, the other two legs are rotating forward. Similarly, when front-right and rear-left legs are upshifting, the other legs are advancing.

 The walking sequence of robot

Servo movement control  I calibrated the rotation angle of each servo motors in each step of the walking sequence, and set a delay between each step to make the robot walk more stably.

Conclusion  So far I have assembled my robot and manage to make it move forward with servo control.  What I plan to do is to give it ability to complete more motions. I will start with moving back mechanism, since it’s similar to walking forward mechanism.