Flame 

      

 

Flame is our first fully 3D walking robot with electric actuation. Similar as in Meta, Maxon DC motors are used to actuate several joints: two sagittal ankle joints, two sagittal knee joints, two sagittal hip joints and one lateral hip joint (for sideways foot placement). All the actuated joints in the sagittal plane are implemented with series elastic elements that allow the application of torque control. Next to the actuation, all joint are equipped with incremental encoders that measure all joint angles and indirectly the elongation of the elastic elements.

 

Series elastic actuation

Flame's upper body

   

The upper body holds most of the essential electronics present in Flame. A PC104 computer (with all the required I/O onboard) has a real-time Linux kernel (RTAI) that runs a control loop at a sample rate of 1 kHz. The control loop implements torque and/or position control on all actuated joints depending on the task at hand. Next to this central computer, important electronic components that are found on the upper body are the inertial sensor (from XSens) and the current amplifiers.

 

Overall, Flame weighs approximately 15 kg and is about 1.3 m tall. At the time of writing it walks at a speed of 0.45 m/s and is able to handle stepdown disturbances up to 8 mm. Continuing research is aiming at a wide speed range with both slower and faster speeds, starting and stopping, as well as larger disturbance handling. The main research topic that has been covered with Flame is the synthesis of 3D stable gait with the application of a (simple) sideways foot placement strategy using information from the inertial sensor.

Movies