The proposed device consists of a gravity compensation mechanism to hold its own weight and a force limit element which is developed by ourselves that can ensure the safe interaction between it and the human operator. Since this developed element can be used to control force/torque, and the gravity compensation mechanism enables easy movement of the device, a force rendering device is built.

Traditional force rendering devices usually use a force/torque sensor to measure interaction force/torque which increases the cost also introduces a delay caused by the control loop, the proposed device has intrinsic safety property due to its working principle and mechanical safety does not require a control loop to check if the interaction force exceeds the limit.

The gravity compensation mechanism employs a spring and a rope to balance the weight according to different configurations of the device adaptively. A strong spring is required to hold the weight and this caused the rope to get stretched and the gravity compensation function can be degraded. To avoid this, a new type of rope that consists of Dyneema rope and another rope was made, experiments show that it can endure high tension while maintaining its length.

In the end, the gravity compensation mechanism and the force/torque limit element together can achieve the force rendering device with safety property.