# Bilateral Teleoperation System with Integrated Position/Force Impedance Control for Assembly Tasks
## 6 Discussion  
The performance of the three different control methods were verified with representative experiments. In the following, we discussed the proposed integrated position/force control method by the experimental data and related literature.  
(1) Compared with the conventional position control (Section 4.1), which has a good performance in free space, the average maximum contact force during the insertion of the proposed integrated position/force control algorithm decreased from 27.35 N to 10.49 N. The results indicate that, during the teleoperation insertion assembly, the proposed method possessed the capacity to pull back the position of the hand toward the center of the hole to alleviate the rigid collisions caused by position errors. This result has a similar situation in the challenging test. Moreover, the contact force was short-lived because the impedance algorithm kept it away from the collision.  
(2) Compared with the manual/automatic mixed control strategy based on Cartesian impedance control, the impedance control-based peg-in-hole assembly shows higher accuracy and lower contact force, and the average maximum contact force decreased from 10.49 N to 6.12 N. However, the disadvantage of the impedance controller is that the method is a fully automatic strategy, and the remote robot cannot be controlled by the operator directly. When the target shape is changed, the impedance controller needs to be re-customized to fit the different situation [41]. This was further verified in the designed challenging task. In a complex motion trajectory such as a curved surface welding task, it is necessary to predefine the desired path in the process of impedance control. This not only makes the design complex, but it is also not suitable for unknown and  
Figure 15: The max contact force in the X and Y axes of ten tests controlled by two methods. Method 1 representatives the master–remote position controller; method 2 represents the designed integrated position/force control method. Those red “\(\times\)” indicate that in this experiment, the remote robot stopped for protection due to excessive contact force.  
changing environments. The proposed method adjusts the position on the basis of human operation. Therefore, the human manipulation was incorporated into the autonomous conductance control loop to combine the human operational initiative and the compliance of impedance control.  
(3) Compared with the traditional hybrid force/position control algorithm which divides the motion space into the force control space and position control space, and has certain requirements for the timing of conversion, when the moment to switch control mode mismatches the instant of the actual environment change, unstable responses may be caused [14]. The proposed integrated position/force control method took the demonstration position as the desired position and, in the same motion direction, the robot executed the combination of operator control commands and local adjustment position commands. There is no process of mode transformation.  
In summary, the proposed method has higher accuracy compared with position control and higher flexibility compared with conductance control. Additionally, it achieves the combination of the operator's initiative and the precision of automatic assembly, and it can alleviate the rigid collisions caused by position errors.