Trunk-type collaborative robot (cobot).
The collaboration between the operator and the robot has two options: holding and maneuvering the end-effector or using a joystick on each direct-drive actuator.
Sensorless excitation of engines employs impedance control.
Gear-less direct drives.
For more detailed info, our article "Synchronized Motion Profiles for Inverse-Dynamics-Based Online Control of Three Inextensible Segments of Trunk-Type Robot Actuators" is a good start at doi.org/10.3390/app11072946.