7.0: Prelude

In earlier chapters, we discussed that a mechatronic system consists of the physical plant, sensors, actuators, and any open- and closed-loop controllers. The physical system (plant), sensors, and actuators belong to physical domain. The control strategy and data processing mechanism are inside the information domain. In this chapter, our focus will be the control systems. We will utilize the techniques introduced in Chapters 2, 3, and 4 to design closed-loop controllers, analyze the closed-loop mechatronic system performance, and then implement the controller into the microcontroller.

Section 7.1 reviews the architecture of a mechatronic system from both structural and hardware points of view. The mechatronic system often uses open- or closed-loop control systems to regulate certain system outputs to its target values [1], [2] or it controls some system outputs to track the desired trajectory [3], [4], respectively. The open- and closed-loop control system architecture and its associated hardware will be discussed by using a few examples. Most mechatronic system components have been introduced in early chapters; this section mainly addresses system level requirements and architectures.

Section 7.2 reviews the microcontroller architecture [5] for implementing the control software. First, it addresses the difference between a microcontroller and a microprocessor. A microcontroller unit (MCU) [5] is essentially a small computer on a single chip. It is designed to manage specific tasks within an embedded system without requiring a complex operating system. By contrast, a microprocessor [6] is a computer processor with the data processing logic and control included on a single integrated circuit (IC) or a small number of ICs. The microprocessor contains the arithmetic, logic, and control circuitry required to perform the functions of a central processing unit (CPU).

Next, the general architecture of a mechatronic microcontroller is discussed. Microcontrollers are the core of mechatronic systems. They can be categorized commonly based on their architecture, data bus width, instructions set, and application scenarios. Last, the section presents the process of selecting a proper microcontroller for designing a mechatronic system. Selecting an appropriate microcontroller for a mechatronic system requires a systematic approach. It is essential to first establish a comprehensive understanding of the mechatronic system requirements and architecture before proceeding with the selection of the microcontroller.

Section 7.3 provides detailed information of a sample microcontroller: Arduino MKR 1000 Wi-Fi [7]. First, we discuss the Arduino family microcontrollers, along with their IDE (integrated development environment) software [8] and the program environment under MATLAB and Simulink [9]. Next, we introduce in detail the Arduino MKR 1000 Wi-Fi microcontroller, including its circuit board, pin layout, detailed electronic circuit, surrounding electronic components, and its core, ARM 32-bit Cortex-M0+ MCU [10]. The intension is to familiarize readers with the microcontroller and its circuit from the hardware point of view and to compares the sample microcontroller (Arduino MKR 1000 Wi-Fi) with the microcontroller architecture discussed in Section 7.2. Last, the MATLAB and Simulink Arduino MKR 1000 Wi-Fi software is discussed in brief along with Arduino UNO Q. A detailed Simulink discussion is provided in Appendices A and B.

Section 7.4 addresses the control system architecture of mechatronic systems. The section will use an example of DC-motor speed control, building on the overall mechatronic system architecture of both hardware and software that are introduced in Section 7.1. We start with the hardware of the DC-motor speed control system, utilizing the Arduino MKR 1000 Wi-Fi microcontroller. In order to make this control system work, an additional DC-motor drive board, the Arduino MKR motor carrier [12], is needed to drive the DC motor and collect the hall-effect speed sensor signal. The Arduino MKR motor carrier board is open source. Its detailed information can be found in [12]. We then present the Simulink motor control software. We show how the motor drive and hall-effect sensor input blocks in the Arduino Simulink support library can be used to develop closed-loop control software utilizing the PID (proportional-integral-derivative) control technique [13].

Section 7.5 introduces a model-based mechatronic system development process, called the V-design process. This process starts with the required mechatronic system specifications or requirements and ends with a design leading to a life-cycle optimized product. For developing the mechatronic system models, this design process starts with a rough mathematical model that leads to a more detailed model, also called a digital twin of the target mechatronic physical system. This model can be used to evaluate closed-loop mechatronic system performances by adding actuator and sensor dynamics, and then considering the detailed physical system dynamics and nonlinearities. A successful design that is validated through simulation now moves to generating a prototype of the mechatronic system, on that is optimized for the system’s life cycle.

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