words)Translational studies on motor control and neurological disorders require detailed monitoring of sensorimotor components of natural limb movements in relevant animal models. However, available experimental tools do not provide a sufficiently rich repertoire of behavioral signals. Here, we developed a robotic platform that enables the monitoring of kinematics, interaction forces, and neurophysiological signals during user-definable upper limb tasks for monkeys. We configured the platform to position instrumented objects in a three-dimensional workspace and provide an interactive dynamic force-field. We show the relevance of our platform for fundamental and translational studies with three example applications. First, we study the kinematics of natural grasp in response to variable interaction forces. We then show simultaneous and independent encoding of kinematic and forces in single unit intra-cortical recordings from sensorimotor cortical areas. Lastly, we demonstrate the relevance of our platform to develop clinically relevant brain computer interfaces in a kinematically unconstrained motor task control of the robot arm, 3) a synchronized interaction force recording system, 4) a strain-gauge grip pressure sensor, 5) an infrared video tracking system to measure three-dimensional joint kinematics (Vicon, Oxford, UK) and an 6) electrophysiology system (Blackrock Microsystems, Salt Lake City, USA). We assessed the versatility and efficacy of our framework by programming a robotic task for monkeys. We configured the robot to position objects in a three-dimensional workspace and trained monkeys to reach and pull on the objects while kinetic, kinematic and neural signals were simultaneously recorded.
Closed-Loop control infrastructureThe IIWA robotic arm features a large workspace (Figure S1) allowing ranges of motion that are compatible with both human and monkey reaches. Additionally, the robotic arm is able to actively lift up to 7Kg of weight, which makes it robust to manipulation by monkeys.We developed a software package that implements a real-time closed-loop control (Figure 2A, 10.5281/zenodo.3234138) configured as a finite state machine. This allows fast configuration of tasks that proceed through several phases, where each phase requires a different behaviour of the robot.In our specific example application, at the beginning of the trial, the robot moves the end effector to a predetermined position in space using impedance joint control. Upon reaching position, the state machine switches to mass-spring damper behaviour (Figure 2A). Stiffness and damping parameters are definable by the user. Variations from this behaviour can be easily configured using our software.