Joint torque sensory feedback is an effective technique for achieving high-performance robot force and motion control. However, most robots are not equipped with joint torque sensors, and it is difficult to add them without changing the joint's mechanical structure. A method for estimating joint torque that exploits the existing structural elasticity of robotic joints with harmonic drive transmission is proposed in this paper. In the presented joint torque estimation method, motor-side and link-side position measurements along with a proposed harmonic drive compliance model, are used to realize stiff and sensitive joint torque estimation, without the need for adding an additional elastic body and using strain gauges to measure the joint torque. The proposed method has been experimentally studied and its performance is compared with measurements of a commercial torque sensor. The results have attested the effectiveness of the proposed torque estimation method.

A joint torque estimation technique utilizing the existing structural elasticity of robotic joints with harmonic drive transmission is proposed in this paper. Joint torque sensing is one of the key techniques for achieving high-performance robot control, especially for robots working in unstructured environments. The proposed joint torque estimation technique uses link-side position measurement along with a proposed harmonic derive model to realize stiff and sensitive torque estimation. The proposed joint torque estimation method has been experimentally studied in comparison with a commercial torque sensor, and the results have attested the effectiveness of the proposed torque estimation technique.

In this paper, we study the problem of door-opening by using a modular re-configurable robot (MRR) mounted on a tracked mobile platform. The main concern of opening a door is how to prevent the internal forces that occur because of the positioning error or the imprecise modeling of the environment, i.e., the door parameters. Most previous research is based on compliant control, which makes the control system rather complicated. In addition, such approaches need expensive force/torque sensor to be implemented. With respect to the multiple working modes of the MRR modules, the complication has been avoided by switching the joints that has axis of rotation parallel to the door hinge to work in passive mode. As a result of this approach, the internal forces between the door and the mobile manipulator will vanish. Simulation results demonstrate the validity and efficiency of the proposed door opening strategy.

In this paper, we study the problem of door-opening by using modular reconfigurable robot (MRR). Based on multiple working mode control of the joint modules of the MRR, we first propose an online mode-switch strategy for all joint modules so that each joint module can be easily determined when it should be switched between active working mode and passive working mode during the door-opening process. Based on the proposed mode-switch strategy, a hybrid control scheme is proposed for door-opening. Simulation results are used to demonstrate the validity and efficiency of the proposed mode-switch strategy and the hybrid control scheme.