Broadcast event-triggered control scheme for multi-agent rendezvous problem in a mixed communication environment

This paper addresses the communication issue encountered by a hybrid controller when finding consensus in terms of the rendezvous target point in a broadcast and communication environment. This issue may result in a high level of computation and the utilization of agent resources when a continuous communication is required by agents to meet convergence requirements. Thus, an event-triggered system was integrated into the design of a broadcast and distributed consensus linear controller using the simultaneous perturbation stochastic algorithm (SPSA). The agent’s movement towards the rendezvous point is based on the broadcast value, whereas the next agent’s state position depends on the distributed local controller output. The communication error obtained during communication between the agent and neighbors is only added to the gradient approximation error of the SPSA if the event-triggered function is violated. As a result, in our model, the number of channel utilizations was lower and the agents’ performances were preserved. The efficiencies and effectiveness of the proposed controller have been compared with the traditional sampling broadcast time-triggered (BTT) approach. The time and iterations required by the broadcast event-triggered (BET) system were less than 40.42% and 21% on average as compared to BTT. The trajectory was not the same—the BET showed scattered movements at the initial stage, whereas BTT showed a linear movement. In terms of the number of channels, 28.91% of channels were preserved during the few hundred iterations. Consequently, a variety of hybrid controllers with event-triggered mechanisms can be proposed for other multi-agent motion coordination tasks

Broadcast and event triggered distributed consensus controller for multi agent motion coordination systems

This paper integrates a multi-agent broadcast controller with an event triggered distributed controller to solve multi agent motion coordination consensus issue. The broadcast controller has been designed by using the Simultaneous Perturbation Stochastic Algorithm. A distributed consensus protocol is adopted with an event triggering function to achieve local consensus among agents with a less number of communication channel usage. Each agent will receive a feedback signal from broadcast controller to update its position from the target while the communication between agent and its neighbours will happen if satisfying the event triggered condition at event instant time. It has been proven that the system can achieve consensus by utilizing the proposed control method. This result shows that at a certain time and iteration the agent can reach the target while reducing the communication channel usage as well as utilization of energy consumption during the process

CO2 laser cutting performance on ultra high strength steel (UHSS)

Evolution of a new breed steel, Ultra High Strength Steel (UHSS), has been adapted by the automotive industry after being used for heavy trucks. Higher tensile strength and improved mechanical properties of UHSS are the main reason for its selection particularly in Body In White (BIW) construction at critical chassis area. Laser cutting process is noted as the final trimming method for this harden material as die pressing resulted as an ineffective process. UHSS cutting performance using CO2 laser with variation on laser power, cutting speed, assist gas type and assist gas pressure was determined to identify the effect of these parameters on the cutting quality. Cutting quality assessment was carried out according to EN ISO 9013 standard where kerf width, perpendicularity and microhardness were evaluated based on parameters set at 1.7 mm thickness of 22MnB5 UHSS boron steel. The quality of these cuttings was evaluated as the results show that thermal exposure dependent on energy density and gas type reflect the outcome where higher thermal exposure introduced bigger kerf with better perpendicularity. It was also found that isothermal effects such as Heat Affected Zone (HAZ) and martensitic transformation were also clearly visible since nitrogen produced a better cutting quality and material integrity consumption at the cutting edge