Delay Sensitive Wireless Protocols for Telerobotics Applications

Abstract

In telerobotics applications, communication delays play a central role in overall system performance, and their minimization is a fundamental problem in this area. In this paper, we consider a master arm on the operator side, and a slave arms (Robot arm) operating in a wireless environment with sensors located on or around this slave arm. Sensor data needs to be transmitted to the operator side to provide feedback, and operator commands must be transmitted to the slave arm to operate it. In a setup like this, minimization of transmission delays is of extreme importance for smooth interactive operation. In the first part of the paper , we evaluate of two alternatives for wireless protocol development and analysis for our Mitsubishi robot RV-2AJ. The first one is the Universal Software Radio Peripheral (USRP) (11) which has an FPGA for baseband processing and other possible low level protocol details. USRP has analog daughterboards for different frequency bands, including 900MHz, and 2.4GHz bands. USRP allows custom protocol development in the physical, and MAC lay- ers, as well as the layers above these two. The second alternative system considered is a powerful microcontroller with an 802.11b controller card (12, 10). In this system, lots of physical layer details are fixed inside the 802.11b controller card, there is no operating system on the microcontroller, but one can generate custom 802.11 packets, and build custom protocols above the MAC layer for delay sensitive telerobotics applications. In the second part of the paper, we present the details of the proposed custom protocol and its implementation on the selected microcontroller board with an 802.11b controller. The proposed custom protocol is compared with standard data communication protocols, and it is demonstrated that the proposed protocol has smaller communication delays. Finally, in the presence of traffic congestion, or/and low received signal strength, it has been also shown that the proposed protocol has significant advantages compared to standard data communication protocols.