Implementation and characterization of a multi-hop 6TiSCH network for experimental feedback control of an inverted pendulum

Abstract

6TiSCH is a technology being standardized at the IETF which brings determinism to low-power wireless communication. In a 6TiSCH network, all communication is orchestrated by a communication schedule. This paper explores the applicability of this new technology to control systems. In particular, we apply it to the inverted pendulum, a canonical control system in which a cart moves along a track to keep a pendulum — which naturally falls over — upright. This paper presents the first characterization and implementation of a closed-loop wireless feedback control network using completely standards-compliant IEEE802.15.4 TSCH technology. First, we implement a control loop in OpenWSN and experimentally evaluate the performance of the network by varying the radio duty cycle, number of hops, and introducing controlled external interference. We show that 100% reliability can be achieved while maintaining latencies well below the critical delay of the system. Second, we use the network on an inverted pendulum system and show that angular deviations from the upright position do not exceed 3 degrees, even in a multi-hop setup. Finally, we discuss the results in detail, and advocate for a co-design of the controller and the networking system.