Reducing Contact Bouncing of a Relay by Optimizing the Switch Signal During Run-Time

Reducing the contact bouncing of electromechanical relays is a key ingredient to increase their switch reliability and overall lifetime. For this reason, this paper presents a control system as well as an optimization algorithm to reduce the kinetic energy of internal relay components by suspending acceleration during each switch cycle. A two-level control of the coil supply voltage is used in order to generate a control signal, which is defined by a certain start time as well as a specified duration. Both values are optimized via a computationally lightweight algorithm using a variant of a particle swarm optimization (PSO), which is a hybrid form of a bare-bone PSO and evolutionary PSO, augmented with dense estimation. Results are presented both qualitatively and quantitatively based on real-world experiments with various sample relays. Using the well-known run-to-run (R2R) algorithm as a baseline, the proposed bouncing optimization algorithm (BOA) reduces the switch on bouncing by 79 % ( $+$ 24 % more than R2R) and the switching off bouncing by 59 % ( $+$ 40 % more than R2R) compared to a conventional switch cycle without bouncing countermeasures. In addition, the proposed algorithm's capability of self-adapting to changing environmental circumstances is validated experimentally. Note to Practitioners —Contact bounce increases relay wear. It is therefore desirable to reduce this. For this purpose, many mechanical optimizations have already been carried out. In this work, however, a software solution (BOA) is presented in which an online optimization algorithm is used to design the control signal of the relays in such a way that bouncing is reduced. The acceleration of the contacts is briefly suspended during the switching process, so that the contacts collide with less kinetic energy and, therefore, bounce less -as in the case of elastic impact. With BOA, it is possible to reduce the duration of bouncing by up to 79% during extensive tests. A transfer to various types of relays seems possible, but two points are critical for productization: First, a microcontroller is needed for implementation, which can significantly increase the manufacturing costs of a product. Secondly, a measurement signal of the load side of the relays is necessary, which can be technically challenging.