A servo system is one in which the system’s error (in position, speed, or torque) is corrected through the use of a feedback device that compares the system’s actual performance with its commanded performance. What makes a motor a servo motor, then, has less to do with its construction and operation, and more to do […]
FAQs + basics
FAQ: How do linear stepper and linear ultrasonic piezo motors differ?
There are a number of ways in which piezo ceramics can be used to create linear motion, providing any combination of high speed, long travel, and high force. Two common types are linear stepper and linear ultrasonic piezo motors. Both use the inverse piezoelectric effect to activate a rod or pusher and create linear motion, […]
FAQ: Where are linear stepper piezo motors suitable?
There are several types of piezo motor that provide linear motion, with one of the most widely used being the linear stepper piezo motor. These devices harness the coordinated motion of multiple piezo elements to produce virtually unlimited travel with high resolution and very high stiffness. Construction and operation In the linear stepper design, multiple […]
FAQ: What are servo feedback gains, overshoot limits, and position error limits?
Servo tuning can be accomplished by several methods, but the most common way is to use a PID algorithm. The PID algorithm uses three feedback gains—proportional gain, integral gain, and derivative gain—to compare the commanded position (or velocity) with the actual value and issue commands to correct errors between the two. Feedback gains determine how […]
FAQ: Don’t piezo motors get hot?
Traditional electromagnetic servo and stepper motors experience electrical and mechanical losses, which result in heat generation and can limit their performance. Piezo motors also experience losses and heat generation, but since they operate via the piezoelectric effect and have no mechanical parts, their performance is affected by different factors. Due to their low conductivity and […]
FAQ: What are flexure guided piezo actuators?
When a voltage is applied to a piezoelectric material, it generates motion and force due to the expansion or contraction of the material. Piezo actuators take advantage of this effect, incorporating piezoelectric materials into useful devices for generating very small, high-frequency movements and producing relatively high forces. Flexure guided piezo actuators incorporate mechanical hinges (flexure […]
FAQ: Where are ultrasonic piezo motors suitable?
Ultrasonic piezo motors harness oscillations induced in a piezoelectric material to produce motion, which can be either rotary or linear. Their design and operation are relatively simple but allows them to achieve very high accelerations and speeds, and to produce high holding forces when no current is applied. Construction and operation For rotary motion, the piezo […]
FAQ: How are the controls for servo motors tuned?
Servo motors are used in closed loop systems and operate based on error feedback—the comparison of a target value to the value actually reached by the motor/load. Because mechanical systems have inertia and compliance, the target value is rarely achieved on the first position command—hence, the need for feedback and correction commands. Servo tuning is […]
FAQ: What is settling time in a motor-driven servo system?
One of the unique characteristics of servo systems is that they operate in closed-loop mode. This means they use feedback—from a resolver or encoder on the motor, and sometimes from an encoder on the load—to compare the commanded value (typically position, speed, or torque) with the value that was actually reached. Based on this feedback, […]
How are servo motors physically different from motors that run open loop?
A servo motor is, by definition, one that runs closed-loop, with feedback to control the motor’s position, speed, or torque. Of motors that run open-loop, with no feedback device, stepper motors are the most common type. Despite their different control mechanisms, stepper and servo motors have a few characteristics in common. First, they both have […]