The Advantages and Working of a Servo Motor

Servo control, which is known as "motion control" or "robotics" is used in industrial processes to move a specific load in a controlled fashion. These systems can utilize either pneumatic, hydraulic, or electromechanical actuation technology. The choice of the actuator type (i.e. the device that provides the power 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. Servo Motors are the actuators used in electromechanical systems. Through the interaction of electromagnetic fields, they generate power.

Servo Motor Advantages

Servo motors with related controls provide very precise and repeatable control of both position and velocity, and its various feedback parameters allow users to closely monitor the dispensing process and detect any abnormalities before they can become major problems. There are three main advantages to servo drive technology in adhesive and sealant dispensing equipment:

1. Servo drive motors allows you to have preset, multi-segment shot profiles, with each segment having its own material volume and flow rate, and with the ability to smoothly blend the motion of each segment into the next one in the profile.  The user can then select from among these preset profiles before initiating the dispense cycle.

2. Servo technology also allows you to continuously vary the material flow rate during the dispense cycle based upon a command reference from the process control.  This allows the user to either apply a continuous bead of material with varying bead widths, or conversely, to maintain the same bead width despite changes in the applicator's linear speed, for example when a robot slows down to negotiate a complex curve.

3.  A major advantage to servo control is its ability to reliably maintain the commanded volumetric flow rate of material despite changes in the physical conditions of the dispensing system or its environment.  Examples of these types of changes are variations in material viscosity, and therefore in the back pressure it generates during the dispense cycle, due to such things as variations in ambient temperature or differences in batches of material; variations in the plant utilities supplied to the dispensing equipment, such as air pressure or electrical voltage; and load changes due to physical wear on the dispensing equipment as it ages.  The servo drive simply increases or decreases the amount of current it supplies to the motor as required to maintain the commanded material flow rate, up to the current limits of the drive.  If those limits are ever exceeded, the drive generates a fault and stops the cycle, which prevents the customer from unknowingly making out of spec parts.

Working of a Servo Motor

Servo motors are utilized to control position and speed very precisely, but in an easy case, only position may be controlled. Mechanical position of the shaft can be sensed by using a potentiometer, which is coupled with the motor shaft through gears. The current position of the shaft is converted into electrical signal by the potentiometer, and the compared with the command input signal. In modern servo motors, electronic encoders or sensors are used to sense the position of the shaft.

Command input is given according to the required position of the shaft. If the feedback signal differs from the given input, an error signal is generated. This error signal is then amplified and applied as the input to the motor, which causes the motor to rotate. And when the shaft reaches to the required position, error signal becomes zero, and hence the motor stays standstill holding the position.

The command input is given in the form of electrical pulses. As the actual input applied to the motor is the difference between feedback signal (current position) and applied signal (required position), speed of the motor is proportional to the difference between the current position and the required position. The amount of power required by the motor is proportional to the distance it needs to travel.