# Development of a Hardware-in-the-Loop Platform for a Teleoperation Flexibility Robotic System
## 5 Experiments  
After ensuring the stability of the proposed method, the effectiveness of teleoperation control of the CDHR robot was tested experimentally to evaluate the performance of the system. The experiment involved a local site and remote site, as shown in Figure 15. The local site included the haptic device, a laptop, and a Zigbee module. The laptop was used to communicate with the haptic device and send data to the CDHR robot through the Zigbee protocol. The remote site consisted of a cable robot, an electrical cabinet, and an embedded computer. The Jetson Nano computer (NVIDIA, Santa Clara, CA, USA) was used to implement the algorithm of the CDHR robot. Then, the position signal after using the position method was sent to the electrical cabinet, which housed the distributed control system Control Area Network (CAN) and six-driver AC Servo. The CDHR robot was assembled using AC motors to control its motion through cables. Figure 14: Response of the slave system: (**a**) position along X axis in simulation and (**b**) force generated using the haptic device. The details of the teleportation system are depicted in Figure 15. First, the operator holds and moves the Novint Falcon to generate the desired trajectory planning. These signals are converted into the reference position of the CDHR robot using the mapping method and sent to the remote site through the Zigbee communication channel. Second, the Jetson Nano solves the inverse kinematics using the Jacobian method to obtain the joint angles. These data are transmitted to the distributed control system, which consists of an STM32F407 and a controller board to operate the robot. This module uses the CAN bus protocol; this protocol is based on the application involving the car vehicle and can reduce the calculated volume and improve the performance of the system. Finally, the encoder sends joint angle feedback to the microcomputer, which is then presented on a graphic user interface (GUI). To demonstrate the effectiveness of the teleoperation system, the experiment is performed by holding the haptic device in the singularity area. The results are depicted in Figure 16.  
To evaluate the effectiveness of the proposed method in the experiments, the haptic device was pulled into the singularity area multiple times, which is indicated by the blue circle in Figure 16a. The setpoint is highlighted in the black color, and setpoint data were collected through the API for communicating with the haptic device. The solid red line  
Figure 16: Results of experiments: (**a**) planning of Novint Falcon using haptic algorithm, and (**b**) response signal of CDHR robot along \(X\)-axis. Figure 15: Experimental testbench. denotes the position of the end-effector of the CDHR robot, which was calculated from the encoder signals of the AC motor and the forward kinematics of the robot. In the area covered by the blue circle in Figure 16a, the robot seems to be immobile when its position does not follow the setpoint, and the overshooting phenomenon is avoided. The system switches to the haptic mode to generate a force that is applied to the palm of the operator for returning the device to the safe area. According to the results of the simulations and experiments, the proposed methods are not only effective but also resolve the challenges resulting from the inverse kinematics problem, the difference between the two workspaces, and singularity of the teleoperation system. Estimates of the forces generated when the operator attempts to pull the master device to stop it moving outside the workspace are presented in Figure 17. Because the operator pulls the haptic device along the X-axis, the magnitude of force along this axis is greater than the sum of the forces along the Y- and Z-axes, which ensures device stability. According to Figure 17, the estimated force along the X axis is 4 N, and those along the Y- and Z-axes are 1 N. At this point, the slave robot is immobile until the master device is inside the safety area.