PAL Robotics

PAL Robotics has been making humanoid robots since 2004 and develops products for research as well as social robotics, intralogistics and retail.

I worked with PAL Robotics to design “Kangaroo”, a bipedal robot capable of walking and jumping. The design of this robot was very much a team effort but basically I designed the leg and ankle, and also assisted with the hip roll/pitch/yaw design. 

The leg incorporates a linkage mechanism to produce leg extension in a direction very close to a straight line. This line of action intersects the hip pitch axis, meaning that the leg length and hip swing motions are decoupled and don’t produce negative work by fighting against each other.

Because of its linkage-driven design the gear ratio of the leg length actuation is non-linear, and we used this to our advantage. By adjusting the link lengths of the leg mechanism, the gear ratio profile can be optimised to achieve the necessary speeds and torques for jumping but require only low power whilst standing and walking.

The design uses ball screw actuators with custom force sensors. These are backdrivable, efficient and produce very nice force control. All the actuators are packaged around the hip resulting in a leg with very low inertia.