Palki Technology Co.,Ltd.

This is a small and low-cost type of computer that runs a program stored in non-volatile memory. Configuring a microcontroller for a system generally requires an experienced programmer, and closing loops such as position and velocity can be quite difficult. Often, when one designs a servo system using a microcontroller, one will have the amplifier/drive close the desired loops, while the microcontroller simply sends particular commands back to the amplifier. These commands may be dependent on inputs into the microcontroller (sensors, switches, etc).

Controllers come in a variety of forms which people choose based on cost, performance, convenience, and ease of use. Most controllers fall into the category of Microcontrollers, PLCs, and Motion Controllers. Each is described below.

The controller is the "brains" of a servo system. It is responsible for generating the motion paths and for reacting to changes in the outside environment. Controllers can be something as simple as an ON/OFF switch or a dial controlled by an operator. They can also be as complex as a computer with the ability to actively control multiple servo axes as well as monitor I/O and maintain all of the programming for the machine.

Typically, the controller sends a signal to the drive; the drive provides power to the motor; and the feedback from the motor is sent back to the controller and drive. Feedback from the load is also routed to the controller. The controller analyzes the feedback and corrects for errors by updating the signal to the amplifier. The controller is considered to be the intelligent part of the servo, closing the velocity and/or position loops while the amplifier closes the current loop. However, many amplifiers will close the velocity and/or position loops reducing computational demands from the controller.

Servo control, which is also referred to as "motion control" or "robotics" is used in industrial processes to move a specific load in a controlled fashion. These systems can use either pneumatic, hydraulic, or electromechanical actuation technology. The choice of the actuator type (i.e. the device that provides the energy to move the load) is based on power, speed, precision, and cost requirements. Electromechanical systems are typically used in high precision, low to medium power, and high-speed applications. These systems are flexible, efficient, and cost-effective. Motors are the actuators used in electromechanical systems. Through the interaction of electromagnetic fields, they generate power. These motors provide either rotary or linear motion. Here is a graphical representation of a typical servo system:

This type of system is a feedback system, which is used to control position, velocity, and/or acceleration. The controller contains the algorithms to close the desired loop (typically position or velocity) and also handle machine interfacing with inputs/outputs, terminals, etc. The drive or amplifier closes the inner loop(s) (typically velocity or current) and represents the electrical power converter that drives the motor according to the controller reference signals. The motor can be of the brushed or brushless type, rotary or linear. The motor is the actual electromagnetic actuator, which generates the forces required to move the load. Feedback elements such as tachometers, lvdts, encoders and resolvers, are mounted on the motor and/or load in order to close the various servo loops.

Company designs and manufacturers servo drives and amplifiers for use in servo systems. Servo drives and amplifiers are used extensively in motion control systems where precise control of position and/or velocity is required. The drive/amplifier simply translates the low-energy reference signals from the controller into high-energy signals to provide motor voltage and current. In some cases the use of a digital drive replaces the controller/drive or controller/amplifier control system. The command signals represent either a motor torque, velocity or position and can be either analog or digital in nature. Analog +/-10 VDC command is still the most common reference signal but it is quickly giving way to digital network commands.

The distinction between tachometers and encoders has blurred. Most industrial vendors and customers use: tach, tachometer, digital tachometer, encoder, and incremental encoder interchangeably. Some may use the term encoders to refer to a heavier duty encoder; Avtron uses the terms encoder and tachometer interchangeably.

The original distinction between tachometers and encoders was that tachometers were used for velocity indication and control only, and could not provide position information.

Only the (older) DC/analog tachogenerator style of tachometer had this limitation; all modern tachometers have quadrature outputs which are used for velocity, position, and direction measurements, making them effectively encoders.

Also offers digital to analog converters to provide analog output from modern digital encoders. This enables customers who have older analog drives to connect Avtron digital encoders to their drives. Replacing analog tachogenerators eliminates the maintenance associated with brushes and bearing wear. For more details, see Special Encoder Applications.