PID control system analysis, design, and technology

Designing and tuning a proportional-integral-derivative (PID) controller appears to be conceptually intuitive, but can be hard in practice, if multiple (and often conflicting) objectives such as short transient and high stability are to be achieved. Usually, initial designs obtained by all means need to be adjusted repeatedly through computer simulations until the closed-loop system performs or compromises as desired. This stimulates the development of "intelligent" tools that can assist engineers to achieve the best overall PID control for the entire operating envelope. This development has further led to the incorporation of some advanced tuning algorithms into PID hardware modules. Corresponding to these developments, this paper presents a modern overview of functionalities and tuning methods in patents, software packages and commercial hardware modules. It is seen that many PID variants have been developed in order to improve transient performance, but standardising and modularising PID control are desired, although challenging. The inclusion of system identification and "intelligent" techniques in software based PID systems helps automate the entire design and tuning process to a useful degree. This should also assist future development of "plug-and-play" PID controllers that are widely applicable and can be set up easily and operate optimally for enhanced productivity, improved quality and reduced maintenance requirements

Evolutionary learning and global search for multi-optimal PID tuning rules

With the advances in microprocessor technology, control systems are widely seen not only in industry but now also in household appliances and consumer electronics. Among all control schemes developed so far, Proportional plus Integral plus Derivative (PID) control is the most widely adopted in practice. Today, more than 90% of industrial controllers have a built-in PID function. Their wide applications have stimulated and sustained the research and development of PID tuning techniques, patents, software packages and hardware modules. Due to parameter interaction and format variation, tuning a PID controller is not as straightforward as one would have anticipated. Therefore, designing speedy tuning rules should greatly reduce the burden on new installation and ‘time-to-market’ and should also enhance the competitive advantages of the PID system under offer. A multi-objective evolutionary algorithm (MOEA) would be an ideal candidate to conduct the learning and search for multi-objective PID tuning rules. A simple to implement MOEA, termed s-MOEA, is devised and compared with MOEAs developed elsewhere. Extensive study and analysis are performed on metrics for evaluating MOEA performance, so as to help with this comparison and development. As a result, a novel visualisation technique, termed “Distance and Distribution” (DD)” chart, is developed to overcome some of the limitations of existing metrics and visualisation techniques. The DD chart allows a user to view the comparison of multiple sets of high order non-dominated solutions in a two-dimensional space. The capability of DD chart is shown in the comparison process and it is shown to be a useful tool for gathering more in-depth information of an MOEA which is not possible in existing empirical studies. Truly multi-objective global PID tuning rules are then evolved as a result of interfacing the s-MOEA with closed-loop simulations under practical constraints. It takes into account multiple, and often conflicting, objectives such as steady-state accuracy and transient responsiveness against stability and overshoots, as well as tracking performance against load disturbance rejection. These evolved rules are compared against other tuning rules both offline on a set of well-recognised PID benchmark test systems and online on three laboratory systems of different dynamics and transport delays. The results show that the rules significantly outperform all existing tuning rules, with multi-criterion optimality. This is made possible as the evolved rules can cover a delay to time constant ratio from zero to infinity based on first-order plus delay plant models. For second-order plus delay plant models, they can also cover all possible dynamics found in practice

Performance analysis of robust stable PID controllers using dominant pole placement for SOPTD process models

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordThis paper derives new formulations for designing dominant pole placement based proportionalintegral-derivative (PID) controllers to handle second order processes with time delays (SOPTD). Previously, similar attempts have been made for pole placement in delay-free systems. The presence of the time delay term manifests itself as a higher order system with variable number of interlaced poles and zeros upon Pade approximation, which makes it difficult to achieve precise pole placement control. We here report the analytical expressions to constrain the closed loop dominant and nondominant poles at the desired locations in the complex s-plane, using a third order Pade approximation for the delay term. However, invariance of the closed loop performance with different time delay approximation has also been verified using increasing order of Pade, representing a closed to reality higher order delay dynamics. The choice of the nature of non-dominant poles e.g. all being complex, real or a combination of them modifies the characteristic equation and influences the achievable stability regions. The effect of different types of non-dominant poles and the corresponding stability regions are obtained for nine test-bench processes indicating different levels of open-loop damping and lag to delay ratio. Next, we investigate which expression yields a wider stability region in the design parameter space by using Monte Carlo simulations while uniformly sampling a chosen design parameter space. The accepted data-points from the stabilizing region in the design parameter space can then be mapped on to the PID controller parameter space, relating these two sets of parameters. The widest stability region is then used to find out the most robust solution which are investigated using an unsupervised data clustering algorithm yielding the optimal centroid location of the arbitrary shaped stability regions. Various time and frequency domain control performance parameters are investigated next, as well as their deviations with uncertain process parameters, using thousands of Monte Carlo simulations, around the robust stable solution for each of the nine test-bench processes. We also report, PID controller tuning rules for the robust stable solutions using the test-bench processes while also providing computational complexity analysis of the algorithm and carry out hypothesis testing for the distribution of sampled data-points for different classes of process dynamics and non-dominant pole types.KH acknowledges the support from the University Grants Commission (UGC), Govt. of India under its Basic Scientific Research (BSR) schem

Tuning and auto-tuning of fractional order controllers for industry applications

This paper deals with the design of fractional order PI²Dμ controllers, in which the orders of the integral and derivative parts, λ and μ, respectively, are fractional. The purpose is to take advantage of the introduction of these two parameters and fulfill additional specifications of design, ensuring a robust performance of the controlled system with respect to gain variations and noise. A method for tuning the PI²Dμ controller is proposed in this paper to fulfill five different design specifications. Experimental results show that the requirements are totally met for the platform to be controlled. Besides, this paper proposes an auto-tuning method for this kind of controller. Specifications of gain crossover frequency and phase margin are fulfilled, together with the iso-damping property of the time response of the system. Experimental results are given to illustrate the effectiveness of this method

Microcontroller Implementation of Digital Pid Controller

A proportional-integral-derivative (PID) controller is widely used in industrial control systems to get the desired response by feedback. In this project, we attempt to implement a digital controller in a microcontroller. The primary difference between a digital controller and an analogue controller is that with a digital controller the actual value is not measured continuously, rather it is periodically sampled at some fixed time interval. To study the issues in implementing a digital PID controller in Arduino microcontroller is the main objective of the project. Once the implementation issues are solved then one can tune the Kp, Kd and Ki gains of the PID controller. Based upon the error occurred and by changing the values suitably, the required output from the system can be obtained. In this project, PID controllers with input and output features are implemented in Arduino and its frequency response is studied in order to adjudge whether the implementation is correct or not. Two methods are used for generating the PID controller output. One by using a properly tuned RC filter that filters out the PWM signal generated by the Arduino and the other by using a digital to analog converter from the digital output of the Arduino

Configuration, Programming, Implementation, and Evaluation of Distributed Control System for a Process Simulator

Abstract A common industrial distributed control system (DCS), DeltaV, is configured and programmed to control and monitor the Nuclear Process Control Test Facility (NPCTF). A cabinet which holds the hardware of the DelatV DCS system, including programmable logic controller (PLC), power supplies, input/output (I/O) cards, terminals, and relays are configured and wired to field devices of NPCTF. A workstation and HMI screen are configured and setup. To implement the main functions of NPCTF in the DelatV system, the programming architecture is designed in the DelatV system. The main control and monitoring functions of NPCTF are programmed using industrial languages of Function Block Diagram (FBD) and Sequential Function Chart (SFC) by IEC61113-3. Safety interlocks are added in the program to protect the NPCTF devices from damage. A HMI is developed to operate and monitor the NPCTF. Through the HMI, the operator can monitor the parameters of process of NPCTF, operate the NPCTF, change parameters of the controller, and force the devices. The process model of SG (Steam Generator) Tank level control is developed using the MATLAB System Identification tool. The model is taken as an example to demonstrate the process of analysis and design the controller of process control. PID is used as the controller algorithm. The main control and monitoring functions of NPCTF in the DeltaV system are commissioned, tested and evaluated. The evaluation results conclude that the DelatV DCS system can control the NPCTF to achieve the main functions of the NPCTF

Tuning of PID controller for higher order system

PID controllers have been widely used in process control industries because of its implementational and tuning advantages. It is mainly used because of its relatively simple structure and robust performance. It seems conceptually very easy to achieve multiple objectives such as short transients and high stability, but tedious in practice. The speed of the response of the system is inversely proportional to the time constant of the dominant pole of the plant. Thus, it is advisable to design such a plant which has pole very near to the origin. Better responses can be found in different systems with different dynamics, like those with low order or high order, monotonic or oscillatory responses and large dead time or small dead time. Tuning of PID controllers for first order plus dead time is very simple and common in practice. Many methods have been found out which can generate the algorithm for first order plus dead time model, but first order plus dead time model is unable to generate peaks for monotonic processes

High-performance series elastic actuation

textMobile legged robots have the potential to restructure many aspects of our lives in the near future. Whether for applications in household care, entertainment, or disaster response, these systems depend on high-performance actuators to improve their basic capabilities. The work presented here focuses on developing new high-performance actuators, specifically series elastic actuators, to address this need. We adopt a system-wide optimization approach, dealing with factors which influence performance at the levels of mechanical design, electrical system design, and control. Using this approach and based on a set of performance metrics, we produce an actuator, the UT-SEA, which achieves leading empirical results in terms of power-to-weight, force control, size, and system efficiency. We also develop general high-performance control techniques for both force- and position-controlled actuators, some of which were adopted for use on NASA-JSC's Valkyrie Humanoid robot and were used during DARPA's DRC Trials 2013 robotics competition.Electrical and Computer Engineerin

PID Controller for Vibration Reduction and Performance Improvement of Handheld Tools

This paper proposes a PID Controller to mprove handheld tools performance and at the same time reduce vibration occurs during its operation. Two experiments has been setup to record vibration of handheld drill using accelerometer placed at certain points of the hand drill. Through experiment, the obtained data was analyzed using Fast Fourier Transform (FFT) and Operational deflection shape (ODS) technique and the data being verify which gives the natural frequency at 476.07Hz which is 5.7% higher that theoretical value. From the data the PID controller is designed and tunes using Ziegler Nichols method which gives peak amplitude at 0.0144 and settling time at 0.45s. From the result it is believed that this proposed controller can reduce the vibration and give good improvement to the handheld tool performance