Robot Dog Part 2: Leg Redesign
Aaed Musa, a robotics builder, explains how he redesigned the TOPS robot dog’s leg, moved its motors to CAN bus, and tested its gait, jumping, and load capacity.
In this talk
- 0:21
Redesigning the leg
TOPS stands for Traverser of Planar Surfaces, and the first installment covered a test leg and inverse kinematics. For this redesign, Musa aimed to remove limit switches, make the leg more compact and lighter, and simplify its construction. The new leg weighs just under 3 kilograms, about 0.4 kilograms less than the previous version.
- 2:09
Switching to CAN bus
Musa changed motor communication from UART to CAN bus because his microcontroller has only eight of the 12 serial ports needed to control all the robot’s motors. CAN bus connects the motors over two wires, reducing wiring. Without an official Arduino CAN library for his ODrive controllers, he cannot read absolute encoder positions, so he manually moves the leg to a reference position and uses built-in physical limits for homing.
- 3:16
Updating the gait
Musa modified the stepping path to use a full sine wave followed by a smaller one, drawing inspiration from Stanford Doggo. He added settings for ordinary walking, larger steps, faster running, and movement sideways or backward.
- 4:00
Testing jumps and load
A loose belt on the knee actuator initially prevented the leg from rising again; adding an idler pulley and reprinting parts fixed the issue. Faster up-and-down motion produced bouncing and then jumps, ranging from repeated small hops to a single larger leap. Scale tests suggested the leg could support about 13 pounds.
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