#Piezo electric motors free

The expansion of this group moves the unlocked 'locking' group along the motor path. Next, the 'motive' crystal group is triggered and held.

First, one group of 'locking' crystals is activated to lock one side and unlock other side of the 'sandwich' of piezo crystals.

The actuation process of the inchworm motor is a multistep cyclical process: Stepping actions Piezoelectric 'inchworm' motor Inchworm motors can achieve nanometre-scale positioning by varying the voltage applied to the motive crystal while one set of locking crystals is engaged.

#Piezo electric motors free

A normally free type allows free movement when unpowered but can still be locked by applying a voltage. The non-powered behaviour of this piezoelectric motor is one of two options: 'normally locked' or 'normally free'. The motive group, sandwiched between the other two, provides the motion. These piezoelectric motors use three groups of crystals-two 'locking', and one 'motive' that permanently connects to either the motor's casing or stator (not both). The inchworm motor uses piezoelectric ceramics to push a stator using a walking-type motion. 1: Stepping stages of 'Normally Free' motor An exceptionally high-torque 'hybrid transducer' ultrasonic motor uses circumferentially-poled and axially-poled piezoelectric elements together to combine axial and torsional vibration along the contact interface, representing a driving technique that lies somewhere between the standing and traveling-wave driving methods. Later designs by Sashida and researchers at Matsushita, ALPS, and Canon made use of traveling-wave vibration to obtain bi-directional motion, and found that this arrangement offered better efficiency and less contact interface wear. Some of the earliest versions of practical motors in the 1970s, by Sashida, for example, used standing-wave vibration in combination with fins placed at an angle to the contact surface to form a motor, albeit one that rotated in a single direction. Two different ways are generally available to control the friction along the stator-rotor contact interface, traveling-wave vibration and standing-wave vibration. The most obvious difference is the use of resonance to amplify the vibration of the stator in contact with the rotor in ultrasonic motors. Ultrasonic motors differ from other piezoelectric motors in several ways, though both typically use some form of piezoelectric material. Common applications of piezoelectric motors include focusing systems in camera lenses as well as precision motion control in specialised applications such as microscopy. The main benefits of piezoelectric motors are the high positioning precision, stability of position while unpowered, and the ability to be fabricated at very small sizes or in unusual shapes such as thin rings. The maximum operating temperature is limited by the Curie temperature of the used piezoelectric ceramic and can exceed +250☌. This extends their usefulness to applications that cannot use traditional electromagnetic motors-such as inside nuclear magnetic resonance antennas. This provides a maximum linear speed of approximately 800 mm per second, or nearly 2.9 km/h.Ī unique capability of piezoelectric motors is their ability to operate in strong magnetic fields.

High response rate and fast distortion of the crystals also let the steps happen at very high frequencies-upwards of 5 MHz. Manufacturers claim precision to the nanometer scale. This, combined with the minute scale of the distortions, gives the piezoelectric motor the ability to make very fine steps. The growth and forming of piezoelectric crystals is a well-developed industry, yielding very uniform and consistent distortion for a given applied potential difference. Piezoelectric motors typically use a cyclic stepping motion, which allows the oscillation of the crystals to produce an arbitrarily large motion, as opposed to most other piezoelectric actuators where the range of motion is limited by the static strain that may be induced in the piezoelectric element. Examples of types of piezoelectric motors include inchworm motors, stepper and slip-stick motors as well as ultrasonic motors which can be further categorized into standing wave and travelling wave motors. An electrical circuit makes acoustic or ultrasonic vibrations in the piezoelectric material, most often lead zirconate titanate and occasionally lithium niobate or other single-crystal materials, which can produce linear or rotary motion depending on their mechanism. Ī piezoelectric motor or piezo motor is a type of electric motor based on the change in shape of a piezoelectric material when an electric field is applied, as a consequence of the converse piezoelectric effect. Two piezoelectric crystals are visible that provide the mechanical torque. Insides of a slip-stick piezoelectric motor.