Reference Velocity Tracking Research Articles

Safe Region Multi-Agent Formation Control With Velocity Tracking

This paper provides a solution to the problem of safe region formation control with reference velocity tracking for a second-order multi-agent system without velocity measurements. Safe region formation control is a control problem where the agents are expected to attain the desired formation while reaching the target region and simultaneously ensuring collision and obstacle avoidance. To tackle this control problem, we break it down into two distinct objectives: safety and region formation control, to provide a completely distributed algorithm. Region formation control is modeled as a high-level abstract objective, whereas safety and actuator saturation are modeled as a low-level objective designed independently, without any knowledge of the former, and being minimally invasive. Our approach incorporates connectivity preservation, actuator saturation, safety considerations, and absence of velocity measurement from other agents with second-order system dynamics which are important constraints in practical applications. Both internal safety for collision avoidance among agents and external safety for avoiding unsafe regions are ensured using exponential control barrier functions. We provide theoretical results for asymptotic convergence and numerical simulation to show the approach’s effectiveness.

A novel brain-inspired approach based on spiking neural network for cooperative control and protection of multiple trains

The ongoing challenge of addressing critical issues related to intelligent cooperative control and active protection persists due to the absence of a comprehensive and efficient integrated solution. To address this challenge, this paper introduces a brain-inspired controller that emulates the collaborative functionalities of various brain regions, harnessing the power of spiking neural networks. The controller’s primary tasks include reference velocity tracking, cooperative control, and active protection, with a special focus on cooperative protection within distinct operational modes. Furthermore, the fundamental principles of incorporating spiking neural networks into train control, such as coding and decoding mechanisms, are expounded. The overarching controller is partitioned into two principal functional segments. The first segment involves emulating the prefrontal cortex (PFC) for reference velocity tracking and active protection against overspeed and collisions through motor control and movement planning. The second segment employs a cerebellum-inspired network for cooperative control. Additionally, the brain-inspired network introduced in this study undergoes training utilizing biologically-inspired mechanisms, incorporating dopamine and pertinent teaching signals to facilitate realistic synaptic modifications. Simulation results in several scenarios validate the proposed approach.

모델 예측 제어를 이용한 높은 질량 중심을 가지는 전방향 이동 로봇의 진동 저감 제어

Autonomous mobile robots equipped with long-stroke lift modules have been developed to assist human workers to transport high positioned heavy objects in the field of logistics. A large amount of rolling vibration during acceleration or deceleration when driving is inevitable for a robot with a high center of mass and low stiffness mechanism. In this study, the simultaneous control of reference velocity tracking and vibration reduction, only using driving motors, is proposed based on a suspended cart-pole inverted pendulum model that combines velocity and vertical vibration motion. A model predictive controller was adopted to account for constraints that prevented the object from slipping when placed atop the lift by saturating the magnitude of the rolling angular acceleration. The simulation results verified that the residual vibration time and magnitude significantly decreased with the proposed controller compared to the controller accounting for driving velocity alone. Additionally, object slippage prevention was ensured with taking minimal loss of the reference velocity tracking performance.

Switched Optimal Control of a Heavy-Duty Hybrid Vehicle

This work investigates the fuel energy and emission reductions possible with the hybridization of a Class 8 tractor-trailer. The truck tractor has two drive axles: one powered by an internal-combustion-engine-based powertrain (CP) and the other powered by an electric powertrain (EP) consisting of an electric drive system supplied by a battery pack, resulting in a through-the-road hybrid. The EP has two modes of operation depending on the direction of power flow: motoring/battery discharging and generating/battery recharging. Switched optimal control is used to select between the two modes of EP operation, and a recently developed distributed switched optimal control is applied. The control is distributed between the CP, the EP, and the vehicle motion operation components. Control-oriented, component-specific power flow models are set forth to describe the dynamics and algebraic relationships. Four different tractor-trailers are simulated: the original CP and three hybrids with engine sizes of 15 L, 11 L, and 7 L. Simulations are performed over a short test cycle and two regulatory driving cycles to compare the fuel use, total energy, and emissions. Results show that the hybrids have reduced fuel use, total energy, and emissions compared to the original CP; the reductions and reference velocity tracking error increases as the engine size is decreased. Particularly, fuel use is reduced by at least 4.1% under a charge sustaining operation and by 9.8% when the battery energy can be restored with an off-board charger at the end of the cycle.

Double-Loop Sliding Mode Controller with An Ocean Current Observer for the Trajectory Tracking of ROV

To solve the trajectory tracking problem of insufficient response and the large tracking error of remotely operated vehicles (ROVs) under the interference of large ocean currents, this paper proposes a double-loop sliding mode controller with an ocean current observer. The designed controller consisted of an outer-loop controller (the position controller) and an inner-loop controller (the velocity controller): the outer controller was designed by the position error, and a reference velocity was created for the inner loop to achieve accurate positioning and attitude tracking. The reference control input was treated as a new target to design the inner-loop controller, enabling the ROV to achieve accurate reference velocity tracking. Based on the theoretical idea of active disturbance rejection control, a kinematic equation-based ocean current observer was designed to estimate and compensate for large unknown currents to ensure accurate trajectory tracking performance under large currents. The simulation results proved that the double-loop sliding-mode control scheme with an ocean current observer always showed good tracking performance, demonstrating the excellent control performance and high robustness of the scheme. Compared with the high-complexity control schemes such as neural network-based PID control or fuzzy sliding mode control, it effectively improves the robustness to ocean current disturbances without increasing the computational effort excessively, and is more practical in ROV systems with limited computational power.

Graph Theoretic Approach to the Robustness of $k$ -Nearest Neighbor Vehicle Platoons

We consider a graph-theoretic approach to the performance and robustness of a platoon of vehicles, in which each vehicle communicates with its k-nearest neighbors. In particular, we quantify the platoon's stability margin, robustness to disturbances (in terms of system H∞ norm), and maximum delay tolerance via graph-theoretic notions, such as nodal degrees and (grounded) Laplacian matrix eigenvalues. The results show that there is a trade-off between robustness to time delay and robustness to disturbances. Both lurst-order dynamics (reference velocity tracking) and second-order dynamics (controlling inter-vehicular distance) are analyzed in this direction. Theoretical contributions are conlurmed via simulation results.

Adaptive Control of Pulse Width Modulation Voltage-Source Rectifier with Disturbance Signals

A nonlinear adaptive controller is proposed for the design of pulse width modulation voltage-source rectifier with disturbance signals of harmonics to achieve reference velocity tracking. The procedure of the robust controller design is developed via improved backstepping method. With the proposed controller, PWM voltage-source rectifiers can guarantee accuracy of output voltage tracking. Global asymptotic stability of the closed-loop system has been proved. The simulation results demonstrate effectiveness of the presented method.

SLIDING MODE PROXIMATE TIME-OPTIMAL SERVOMECHANISM

A discrete-time sliding mode proximate time-optimal servomechanism is developed using nonlinear sliding mode tangent to a reference velocity profile. Instead of a strong nonlinear function causing control chattering in discrete-time, a linear control is designed around the sliding surface. The resulting servomechanism delivers a bounded motion about the sliding surface even in the presence of plant uncertainties. Application results demonstrate accurate reference velocity tracking and uniformly excellent seek performance regardless of seek length via enforced sliding mode.

Nonlinear robust control of a hydraulic elevator: experiment-based modeling and two-stage Lyapunov redesign

In this paper, a robust velocity control problem for hydraulic elevators is investigated. The analysis is divided into two parts, mechanical and hydraulic. A detailed mathematical model for the mechanics is established for the purpose of simulation, but the control system design is carried out with a simplified model reduced from the detailed one. The three important characteristics of a hydraulic elevator, including cylinder friction, pump friction, and pump leakage, are modeled through experiments. The leakage property is characterized as a function of temperature and pressure. A two-stage nonlinear robust controller using the Lyapunov redesign method is established for velocity tracking control. At the first stage, a robust controller for the mechanical part is designed to yield the desired cylinder pressure for reference velocity tracking. At the second stage, a robust controller for the hydraulic part is designed to track the reference pressure generated from the first controller. Simulation results validate that the proposed method is robust in the presence of nonlinearities and uncertainties.