IoT-Enabled Motion Control: Architectural Design Challenges and Solutions

Abstract

Ever-increasing demands for highly-efficient customized manufacturing are driving the development of Industry 4.0. Reconfigurable manufacturing systems based on modular, convertible, and interoperable equipment present a key enabler of the fourth industrial revolution. Besides suitable mechanical design, control of these smart manufacturing resources should facilitate Internet of Things (IoT) integration and reconfigurability. Existing numerical control kernels (NCK)—the major control component for motion control—hinder rapid reconfiguration due to the complexity of their monolithic centralized structure. On the other hand, reconfigurability is naturally promoted by the distributed control paradigm, as proposed by the industrial IoT (IIoT) concept; hence, in this article, we investigate design challenges in distributing the conventional centralized NCK designs used for control of computerized numerical control systems. We introduce an architecture where each axis module is augmented with a networked, IIoT-enabled low-level controller (LLC) that performs local control and exposes a network interface for communication with other LLCs toward executing the desired process. These smart manufacturing resources communicate with an edge-based high-level controller (HLC) that provides the trajectory specification over the network and schedules manufacturing tasks. We investigate real-time and network bandwidth requirements of different mappings of the NCK layers to the LLCs and the HLC, providing design-time tradeoffs for implementing IoT-ready, distributed motion control. We demonstrate feasibility of our approach using industry-grade single-axis robots and low-cost IoT microcontrollers, and show that minimal accuracy impairment is introduced compared to the centralized setup based on ISO 230 and ISO 10791-7 standards.