Control Law Algorithm Research Articles

Autonomous Obstacle Avoidance and Trajectory Planning for Mobile Robot Based on Dual-Loop Trajectory Tracking Control and Improved Artificial Potential Field Method

In order to better meet the practical application needs of mobile robots, this study innovatively designs an autonomous obstacle avoidance and trajectory planning control strategy with low computational complexity, high cost-effectiveness, and the ability to quickly plan a collision-free smooth trajectory curve. This article constructs the kinematic model of the mobile robot, designs a dual-loop trajectory tracking control strategy for position control law and attitude control law algorithms, and improves the traditional artificial potential field method to achieve a good obstacle avoidance strategy for mobile robots. Based on the dual-loop trajectory tracking control and the improved artificial potential field method, the autonomous obstacle avoidance and trajectory planning scheme of the mobile robot is designed, and closed-loop stability verification and analysis are conducted on the overall control system. And through the detailed simulation and experiments, the advantages of the proposed method in trajectory tracking accuracy and motion stability compared to the existing methods are verified, showing good effectiveness and feasibility and laying a good foundation for the application of mobile robots in practical complex scenes.

Reduction of Saturn Orbit Insertion Impulse Using Deep-Space Low Thrust

Orbit insertion at Saturn requires a large impulsive maneuver due to the velocity difference between the spacecraft and the planet. This paper presents a strategy to reduce dramatically the hyperbolic excess speed at Saturn by means of deep-space electric propulsion. The interplanetary trajectory includes a gravity assist at Jupiter, combined with low-thrust maneuvers. The thrust arc from Earth to Jupiter lowers the launch energy requirement, whereas an ad hoc steering law applied after the Jupiter flyby reduces the hyperbolic excess speed upon arrival at Saturn. This lowers the orbit insertion impulse to the point where capture is possible even with a gravity assist with Titan. The control-law algorithm, the benefits to the mass budget, and the main technological aspects are presented and discussed. The simple steering law is compared with a trajectory optimizer to evaluate the quality of the results and possibilities for improvement.

Design of Control Law for Ejection Seat under Adverse Attitudes

The escape performance of ejection seat under adverse attitudes is the key technology for the 4th generation ejection seat, and the design of control law algorithm is the core problem for attitude and trajectory adjustment. A new control law design method was presented. Firstly, a simulation model for the entire ejecting process was established and a control parameter optimization model was designed, through which an optimum parameter set was obtained as the discrete control law. Then, by utilizing multilayer feedback of the error back propagation (BP) algorithm based neural network model, the ultimate continuous control law can be acquired under the whole ejecting conditions. The roll attitude ejecting condition was exampled to design and validate the approached method. The results indicate that the performance of ejection seat by adopting the control law designed by the proposed method is higher than the multi-mode control law and the K3JI-3.5 ejection.

Research on the Design Method of the Starting Process of Main Fuel Control system for Aviation Auxiliary Power Unit

This paper analyzed the main fuel control system of the auxiliary power unit (APU), explored the starting process of the main fuel flow control system control law and control algorithm. Focus on analyzing the interpolation table that is involved in the controller of the starting process, restoring its physical meaning. The design method of the main fuel flow controller for the starting process of the APU is summarized. It’s a valuable reference for the future design of the control system of both aero-engine and auxiliary power unit.

Uncertain Unified Chaotic Systems Control with Input Nonlinearity via Sliding Mode Control

This paper studies the stabilization problem for a class of unified chaotic systems subject to uncertainties and input nonlinearity. Based on the sliding mode control theory, we present a new method for the sliding mode controller design and the control law algorithm for such systems. In order to achieve the goal of stabilization unified chaotic systems, the presented controller can make the movement starting from any point in the state space reach the sliding mode in limited time and asymptotically reach the origin along the switching surface. Compared with the existing literature, the controller designed in this paper has many advantages, such as small chattering, good stability, and less conservative. The analysis of the motion equation and the simulation results all demonstrate that the method is effective.

Clearance of Flight-Control-System Software with Hardware-in-Loop Test Platform

The Indian Light Combat Aircraft has flown more than 2000 flights, including trainer and naval variants, without encountering any major faults in the flight safety-critical fly-by-wire control software. This is partly due to the stringent quality control and rigorous testing of the control-law and air-data-system algorithms carried out on various ground platforms before flight. One of these ground test platforms is the hardware-in-loop test platform (Iron Bird). The processing of tolerance bounds to define the pass/fail criteria is an algorithmic development. It guarantees the correctness of the modules, if the set of inputs generates a set of outputs within processed tolerance bounds. This paper presents the philosophy behind the design of test cases and the tools developed to evaluate the control-law and air-data-system modules on the Iron Bird platform, and the procedure to clear the test results. The computation of tolerance bounds and algorithms for their processing have been evolved over a period based on several criteria, testers’ experience, and the experience gained during various levels of testing of air-data-system and control-law algorithms. This process yielded excellent results, and is accepted as a formal clearance methodology for the onboard safety-critical fly-by-wire system software.

Iterative Learning Control Based on Relaxed 2-D Systems Stability Criteria

This brief develops a new algorithm for the design of iterative learning control law algorithms in a 2-D systems setting. This algorithm enables control law design for error convergence and performance, and is actuated by process output information only. Results are also given from the experimental application to a gantry robot.

Blending optimal algorithm for heliocentric solar sailing

PurposeThe purpose of this paper is to design a solar sail heliocentric transfer orbit which can meet the requirements of control system and capture orbit, and to provide the change of angles for attitude control system.Design/methodology/approachAiming at the problem of solar sail heliocentric transfer orbits design, this paper addresses the derivation of analytical optimal control law. The control laws can realize the combination of the control of each orbit element, but they can only give local optimal solution to meet the practical needs of mission. In order to solve this problem and meet the capture orbit and the attitude control system requirements, the modified genetic algorithm based on the analytical control law is introduced.FindingsThe algorithm addressed by this paper includes results closer to the global optimization, and also can meet the engineering constraints.Practical implicationsThe analytical optimal control law can be applied to the future onboard sail control systems. The blending optimal algorithm is demonstrated to be suitable as a method of preliminary design for solar sail deep space exploration mission.Originality/valueA blending optimal algorithm combining the analytical control law and genetic algorithm is proposed; the algorithm can search for global optimization based on the local optimal results of analytical control law.

RCS Control Study Based on the Model Reference Adaptive Control

For the reusable launch vehicle(RLV), in the cruise stage without power and the initial load phase, due to the aerodynamic pressure is small, and the aerodynamic surface control efficiency is relatively low, it can not achieve the attitude adjustment of the RLV. This design is based on the continuous system, and applies to the model reference adaptive control law algorithms, to achieve the design of the reaction control system(RCS). According to the control torque which is required by the RLV attitude adjustment, the RCS distribution method of mixed-integer programming is used, and the control parameters of the reaction control system is adjusted in real time,thus to achieve the adjustment of the RLV's attitude. Through the software-digital simulation analysis, this method has a good controllability and robustness.At the same time, the stability of the model reference adaptive RCS is analyzed theoretically, and getting a certain amount of stability region.

An Optimal Consensus Tracking Control Algorithm For Autonomous Underwater Vehicles With Disturbances

The optimal disturbance rejection control problem is considered for consensus tracking systems affected by external persistent disturbances and noise. Optimal estimated values of system states are obtained by recursive filtering for the multiple autonomous underwater vehicles modeled to multi-agent systems with Kalman filter. Then the feedforward-feedback optimal control law is deduced by solving the Riccati equations and matrix equations. The existence and uniqueness condition of feedforward-feedback optimal control law is proposed and the optimal control law algorithm is carried out. Lastly, simulations show the result is effectiveness with respect to external persistent disturbances and noise.

A pole placement adaptive control of a rapid thermal processor

Rapid thermal processing (RTP) techniques are often applied in microelectronic technology. The main characteristics of RTP techniques lie in single wafer treatments, fast thermal kinetics at low thermal cost and reduced contamination risks; moreover, many types of reaction can be realized with one single wafer treatment. Problems of measurement and control of space-time temperature profiles have not yet been solved in a satisfactory way; in particular, classical control algorithms (such as PID control) can give bad dynamics to the system if nominal temperature profiles must be modified. Modelling of the thermal behaviour of the process leads to very complex mathematical models. These are the reasons why adaptive control techniques are chosen. A CARIMA model is an interesting input-output model of the thermal processor, whose parameters can be estimated on-line, using an identification scheme which includes supervisory actions. The adaptive control algorithm is a full-state feedback pole-placement law with an adaptive observer. A partial-state reference model was included in the control law algorithm. This type of control law can be implemented even for non-minimum-phase systems, time-varying dynamics, a wrong assumption about the time delay of the system, and when disturbances on the load exist. Experimental results are presented which show a better performance when using an adaptive control strategy

Time-delay compensation in active control algorithms

SummaryIn this paper a direct digital control law algorithm is proposed which in addition to providing tight non-interacting tracking behaviour and excellent disturbance-rejection characteristics, provides for the compensation of finite-time delays in implementation. The control-law algorithm is defined and system stability is proved in the case of multi-input multi-output linear systems. The theory is synthetic and leads directly to the determination of the appropriate controller matrices.The theory is illustrated by the presentation of simulation results in which the aircraft is represented by an analogue computer and the digital control system is implemented on a microprocessor. In the simulation study the controller is required to effect fuselage pitch pointing and vertical translation manoeuvres for the analogue computer representation of the YF-16 aircraft. It is shown that tight non-interacting control is achievable even when the control implemented is delayed by 0·1 seconds.

Bang-bang control law for single-input time-invariant plant

A bang-bang control law for digital-processor implementation is presented which directly implements a nonlinear switching surface for sub-time-optimal control of a single-input time-invariant linear plant of arbitrarily high order with unbalanced control levels. The control law requires a complete state vector and must usually be used with a state estimator or observer. Results are presented for attitude control of a space satellite having a single flexible mode with zero damping. The control law is a development of a predictive controller for a plant comprising cascaded pure integrators in which an analogue model of the plant is repeatedly run ahead in time to predict the future plant behaviour under both signs of extreme drive. The sign of real plant drive is determined using sign-change counts in the model runs. Direct digital implementation of this predictive control law results in unequal, and possibly excessive, periods between plant drive updating. These problems are eliminated in the proposed control-law algorithm by computing the number of sign changes direcly, generating the required sign of plant drive by means of a set of equations involving only the state estimate and the assumed plant-drive levels. Rapid determination of the plant drive is facilitated by the presence of only elementary mathematical operations in the algorithm. Application to a linear plant other than cascaded integrators is facilitated by generating the real-time plant model of the state estimator by transforming the plant state equation to the companion form, ensuring stable control in the neighbourhood of the state origin. In fact, no instabilities have been noted in simulations carried out to date, even for starting points relatively far removed from the origin of the state space.