What is Controller

A controller serves as the brain of a mechatronics system, connecting various electrical, electronic, and mechanical components to enable system functionality. Its primary function is to interpret external input instructions and provide the necessary outputs to activate actuators, thereby fulfilling the given instructions. The controller collaborates with different elements to successfully trigger the actuators and execute the required actions. Controllers can vary depending on the system and operation. Typically, a microcontroller unit (MCU) is used as a relatively simple controller, sometimes embedded as an 'Embedded Controller' within small mechatronics devices. In complex mechatronics systems where multiple machines coordinate harmoniously within a single structure, advanced controllers such as CNC controllers, computers, or programmable logic controllers (PLCs) are employed.

What is a Microcontroller Unit or MCU?

A microcontroller unit (MCU) is a single integrated circuit specifically designed for managing devices and automating certain applications. MCU finds application in various mechatronics systems, including automobile engine control, washing machines, toys, cameras, and security systems. Most MCUs are battery-operated and require minimal power to function. The MCU consists of a small central processing unit (CPU), random access memory (RAM), programmable read-only memory (ROM), and embedded input-output ports (parallel and serial). Due to its dedicated function within a discrete system, the MCU is compact in size, with all components integrated into a single chip. In some cases, an MCU may have additional components like a small LCD or a seven-segment display unit with a keypad for information retrieval and directions. The image below depicts a simple microcontroller and its fundamental structure.

Programming of a microcontroller is typically done using the "C-language," stored in the controller's flash memory, and is reprogrammable. The MCU has various ports to control output elements or actuators connected to it, enabling ON/OFF control through programming. It also receives signals from different sensors connected to programmable ports on the microcontroller. Actuators linked to the MCU's output ports are automatically controlled based on signals received from sensors and instructions addressed in the programming, functioning without human intervention.

Difference between microcontroller and microprocessor:

Microprocessors are generally used with general-purpose CPUs or computers, whereas microcontrollers function as mini-computers to control multiple devices. Unlike microprocessors, microcontrollers include memory devices, input/output ports, and timers. Microprocessors require additional digital components to operate, while microcontrollers act as standalone units. Microprocessor-based devices are typically more complex and expensive, whereas microcontroller-based devices are cost-effective and straightforward. Most pins of a microcontroller can be efficiently programmed, whereas only a limited number of microprocessor pins can be controlled through programming. Additionally, microprocessors typically have higher access times compared to microcontrollers. In summary, a microcontroller directly interacts with coupled sensors and attachments, while a microprocessor connects input/output devices indirectly through an internal bus, uniting multiple hardware components such as RAM, serial ports, and USB ports. For example, a desktop computer commonly utilizes a microprocessor, whereas a washing machine is controlled by a microcontroller.

Advantages of using a microcontroller:

• Functions as a standalone micro-computer without requiring external digital devices.
• Mechatronics systems integrated with MCUs are relatively manageable and easy to maintain.
• Versatile operation due to easily programmable MCU pins. 
• Low operating response time.
• Additional memory devices and input/output components can be easily integrated.
• Compact size and cost-effective compared to other options.

Disadvantages of a microcontroller:

• The structure of an MCU is more complex than a microprocessor.
• Limited to specific purposes only.
• Cannot directly connect to power devices.
• Suitable only for small-scale equipment.

What is a CNC Controller?

Advanced mechatronics controllers are utilized in managing various robotic systems, CNC machines, and complex material handling systems. These controllers can handle almost all tasks within a mechatronics system and possess the capability to store programs in their memory. The key advantage of using advanced mechatronics controllers over microcontrollers is their programmability to manage complex movements and the integration of additional devices or elements into the system. These controllers primarily operate using two types of instructions: programmed instructions stored in controller memory and instructions entered via a connected control panel. Advanced mechatronics controllers, such as CNC controllers, consist of two separate devices—an integrated programmable logic controller (PLC) and a servo amplifier. The PLC may be embedded within the controller or connected externally. The servo amplifier supplies significant voltage to a servo motor for precise control of movements, such as axis movements in CNC machines. The PLC and servo drive mechanism enable a wide range of motions and complex tasks within an advanced mechatronics system while working in coordination with the controller. In some mechatronics systems and CNC machines, stepper motors are used instead of servo motors. These systems rely on a stepper motor and a driver unit to control all movements. The image below illustrates a typical advanced mechatronics system architecture, including a controller, PLC, servo amplifier, and servo motor.

The voltage required to drive stepper or servo motors, provided by the stepper motor driver or servo amplifier, is commanded through a CNC controller, enabling controlled movements. The PLC plays a crucial role in the controller, providing the necessary voltage to different actuators for additional tasks such as activating solenoid valves and running induction motors. After receiving commands from the controller, these tasks are executed flawlessly and monitored by various sensors and feedback elements. Continuous feedback devices like linear scales, encoders, and resolvers serve as position and velocity feedback elements for servo motors, enabling precise position measurement. Proximity switches, limit switches, pressure switches, and float switches are among the sensors used to monitor events. For instance, sensor input can be used to detect whether the machine door is open or closed, if the workpiece is correctly positioned, if the cutting tool is clamped, and if the cooling system is operational.