What Is an Ultrasonic Motor?

The abbreviation of UltraSonic Motor is: USM, the earliest application to the camera is Canon EF series lens. The earliest lens equipped with a USM motor was the Canon EF 300 / 2.8L USM. Traditional motors work on the principle of electromagnetics and convert electromagnetic energy into rotational energy. The USM works based on a new principle that uses ultrasonic vibration energy to transform it into rotational energy.

Ultrasonic motor

Before the advent of ultrasonic motors, there were actually piezoelectric motors driven by the vibration characteristics of piezoelectric materials, but their frequency was not limited to the range of ultrasonic waves. William and Brown applied for US patents for "piezoelectric motors" as early as 1948; Bulova Clock & Watch Company developed a tuning fork-driven watch in 1961; Siemens from 1970 to 1972 The two companies, Panasonic and Panasonic, developed linear piezoelectric stepping motors, but they were not widely used at that time because they could not achieve large output forces and efficiency.

American IBM Corporation in 1973

The frequency range of sounds that can be heard by the human ear is between about 20 Hz to 20 kHz, and beyond 20 kHz, frequencies that the human ear cannot recognize are called ultrasound.

So what exactly is an ultrasonic motor? What is the basic working principle? To put it simply, using the piezoelectric material's input voltage will produce deformation characteristics, so that it can generate mechanical vibration of ultrasonic frequency, and then through the design of the friction drive mechanism, so that the ultrasonic motor can be rotated or linear as an electromagnetic motor mobile.

We usually feel noise when the electromagnetic motor is running. This is because the internal structure of the motor generates vibrations, and the vibration frequency is exactly within the frequency range that our ears can feel. The vibration frequency of the ultrasonic motor is designed outside the range that can be heard by the human ear, so when it is running, we can't feel the sound, so we feel very quiet. This is a very important feature of the ultrasonic motor.

year 1987. Canon introduced the first lens equipped with a ring USM: EF 300 / 2.8L USM.

USM ring structure and principle

According to the method of transforming ultrasonic vibration energy, there are three types of USM:

1. Standing Wave Type;

The basic characteristics of USM:

1. It has low torque and high torque output characteristics;

2. Large braking torque;

3. Simple structure;

4. The controllability of motor starting and braking is very good;

5. The turning sound is very low and almost silent.

In addition to the above-mentioned basic characteristics, Canon Ring USM has its own characteristics:

Schematic

6, high efficiency, low power consumption;

7. The ring-shaped motor can be perfectly combined with the mirror body;

8, low speed, especially suitable for the AF drive of the lens;

9, the rotation speed can be arbitrarily controlled in the range of 0.2rpm ~ 80rpm;

10. Electronic MF with adjustable sensitivity can be realized;

11. The working environment temperature is: -30 ~ + 60 .

Canon has announced three specifications of the ring USM:

USM-M1 USM-L1 USM-L2

Dimensions (mm): 62-54 x 10 77-67 x 10 72-63 x 10

For lenses: EF 14 / 2.8L USM; EF 100/2 USM; EF 200 / 2.8L USM; EF 300 / 4L USM; EF 28-80 / 3.5-5.6 USM; EF 28-105 / 3.5-4.5 USM; EF 35-135 / 4-5.6 USM; EF 35-350 / 3.5-5.6L USM; EF 70-210 / 3.504.5 USM; EF 100-300 / 4.5-5.6 USM; EF 50 / 1.0L USM; EF 85 /1.2L USM; EF 200 / 1.8L USM; EF 300 / 2.8L USM; EF 400 / 2.8L USM; EF 500 / 4.5L USM; EF 600 / 4L USM; EF 28-80 / 2.8-4L USM

Weight (g): 26 45 45

Currently USM-M1 and USM-L1 are used, USM-L2 is no longer used.