Robotic Arm for Boston Dynamics’ SPOT

Over the past year our team designed and built a 6 +1 degree of freedom manipulator arm that will be implemented on Boston Dynamics' SPOT Robot. The largest constraints influencing the design of the arm included SPOT’s payload and maximum power draw, as well as the client’s request for the ability to lift 5 pounds. To allow for some flexibility, some requirements were stressed more than others. SolidWorks was used for modeling, while MATLAB facilitated feasibility calculations throughout the design process. For arm movement, Robotic Operating Software (ROS) is used with a wireless gaming controller that can jog individual joints, or move the end effector with inverse kinematics. After the arm was fully assembled, many unknown problems presented themselves during integration: Motor 2 lacked the strength to lift the arm, and joint 3 had disengaging teeth from the worm gear causing slippage to occur at certain torque conditions. Some of the motor controllers also posed significant difficulties, as ROS would interpolate points between the start, and end of a motor’s trajectory. The motor controllers would attempt to do this as well, leading to unwanted behavior.