Evaluation of delay for a musculoskeletal (MSK) robotic system for teleultrasound tasks

Abstract

Teleoperated systems represent a significant contribution to development in medical field. This alternative simplifies a wide variety of complex procedures, including ultrasound examination, without a need of a specialist or in remote geographic areas. In general, remotely-controlled systems show presence of delay which may cause instability during remote-control operation. Although there have been proposed different approaches to overcome this drawback, most potential Teleoperated solutions have target mainly on improving control system robustness without consistent studies on delay sources. Hence, there is still a need for analyzing master-slave communication network for delay and its effects on system functionality. The main objective of this research is to identify how normal operation of a teleultrasound device might be altered by a degraded communication channel, and how to improve system performance. Theoretical, simulated, and experimental methods are employed to monitor system’s functionality. Several aspects such as workspace, kinematics, and dynamics are evaluated to describe Musculoskeletal (MSK) robot. Delay on master-slave system is identified by executing non-predefined sequences. Movements are recorded on video and analyzed in slow motion to determine presence of delay. Moreover, a network analyzer software is employed to measure actual delay on communication channel while running experiments. Information obtained from this tool is used to validate data collected experimentally. Part of this study also is focused on identifying how delay alters normal behavior of teleoperated system. Experimental analysis is carried out by executing predefined sequences. Information about position and delay is collected for each movement. Position mismatch is identified by comparing experimental results with information obtained from a simulated ideal scenario. After data analysis and comparison, a quadratic relationship between delay and the MSK manipulator’s end effector displacement error is identified. Experimental analysis not only confirms that delay alters optimal performance of teleoperated systems but also suggest importance of implementing an improved communication network. A Virtual Local Area Network (VLAN) is applied to isolate the teleoperated MSK system from other devices by creating a dedicated master-slave channel. Improvements of position accuracy achieved with new setup is identified by experimental analysis using predefined sequences. Collected data is compared one more time with a simulated ideal scenario. Statistical analysis reported a linear relationship between delay time and displacement variation, i.e., trend denoted that a larger delay in communication channel will produce a larger position inaccuracy. Results revealed that using a VLAN effectively reduces delay and end effector’s position inaccuracy.