SpaceBok is equipped with an in-house built drive unit. A low ratio planetary gearbox has been placed inside the stator of a powerful DC outrunner. The result is a lightweight, high torque and back drivable actuation unit capable of thrusting Spacebok to a height of 0.4m and in conjunction with the parallel elastic spring to 1.05m.

To minimize the leg inertia, both actuators are located in the shoulder. The kinematics are based on a parallel mechanism, so both actuators contribute to the thrust during a jumping maneuver. Furthermore, springs that act parallel to the actuators can be mounted safely into the carbon tubes. With integrated springs, more efficient repetitive jumping is possible. Additionally, the jump height is increased, which can be helpful to overcome obstacles.

The monocoque carbon body rigidly connects four pantograph legs. To minimize the leg inertia, both actuators are located in the shoulder. The kinematics are based on a parallel mechanism, so both actuators contribute to the thrust during a jumping maneuver. Furthermore, springs that act parallel to the actuators can be mounted safely into the carbon tubes. With integrated springs, more efficient repetitive jumping is possible. Additionally, the jump height is increased, which can be helpful to overcome obstacles.

The electrical hardware is mounted on a stack composed of three levels. The stack can be conveniently removed from the carbon monocoque body to ease maintenance of the system.

The robot is able to perform stable locomotion with all implemented gaits, namely a pronking gait, a static gait, a walking trot and a diagonal sequence walk. It can cope with disturbances such as pushes or small obstacles (8 cm).

This performance enables further research on the platform within different gravitational settings and on a simulated terrain of Mars or the moon.

To reach versatile and robust locomotion, several static and dynamic gaits have been implemented using a virtual model controller.

A pronking gait is designed by simulating a virtual spring when the robot is in ground contact. A static gait, a walking trot and a diagonal sequence walk are designed through predefined gait patterns. The desired torso position is calculated as a weighted sum of the foot positions.

A Virtual Model Controller is used to control the torso pose. The calculated wrench is mapped to the foot forces using a quadratic program.

Jumping in low gravity results in longer flight phases. With a reaction wheel, the pitch angle of the body can be controlled to ensure a safe landing.