Servo Control with Gyro Sensors

High-speed, high-precision Servo Control with Gyro Sensors to Stop Robots immediately

One issue that must be resolved to achieve high-speed, high-precision robot control is reducing the vibration of the robot. Epson has developed servo control that uses an original gyro sensor ("the servo control") to measure robot hand movements, producing technology that enables the robot to move at high speed and stop immediately.

Achieving high speed and high precision

In general, it's necessary to increase the motor capacity of a robot to raise its operation speed. However, when the speed is raised, vibration also increases, which reduces precision. Another trade-off is the waiting time required for the vibration to settle down after the robot stops, a problem that prevents shortening the time of each process. One way to eliminate the vibration is to increase the rigidity of the robot, but this results in higher costs.
Robots generally estimate how the tip of the arm is moving from the angle and angular velocity of the motor, and control operations based on this estimated data. However, the part of the arm further toward the hand from the motor will deflect slightly regardless of how much the rigidity is increased. For this reason, the hand vibration may differ from the estimated value, causing an issue where precision of the arm tip cannot be achieved.

Gyro sensor can be installed due to ultra-compact design

Originally, gyro sensors were used in devices such as car navigation, and their typical size was approximately as big as a thumb. Epson, always seeking to optimize compact and high-precision designs, gathered together sensing technologies from within the company and developed an ultra-compact sized gyro sensor with a volume 1/100 of conventional types. This more compact design enabled the gyro sensor to be installed on the small robot arm. Such an innovative idea of installing a gyro sensor on a robot had never occurred to anyone in the robot industry at the time and was only possible because of Epson's in-house sensing technologies.
The ultra-compact gyro sensor was installed at the tip of the arm, enabling movements to be detected directly and reflected in the control. As a result, data for the swaying of the arm tip was detected accurately, leading to a dramatic reduction in vibration.

Performance improved by enhancing gyro sensor and reconfiguring robot control

Servo control used on early robots was effective in sharply reducing vibration, but there was room for further performance improvement because the frequency bands in which it could be used were limited.First, a new gyro sensor optimized for robot control was developed, enabling the use of frequencies in higher ranges.
Furthermore, some of the robots in which servo control was not installed had their performance improved by retrofitting the functions of servo control. Then, the mechanism of robot control was reconfigured assuming the incorporation of servo control, enabling the successful use of low frequencies as well.
These measures enabled use in both low and high frequency bands, greatly improving the control performance.

Industry first technology

The enhancement of the gyro sensor and the reconfiguration of the robot control dramatically improved the performance of servo control. This enabled the transportation of heavy objects that could not be moved at practical speeds by conventional robots due to high vibration.Servo control is an original Epson technology that enables the production of high-speed, high-precision robots with a slim design, expanding the lineup of robots that can be selected for a manufacturing process. This control technology improves performance as follows:

  1. 1. Accurate robot control that can stop the robot immediately even when it is moving at high speed
  2. 2. Vibration reduction control that can minimize arm swaying even when it occurs during robot operation

Developed from Epson's unique capabilities

Servo control was developed not simply by increasing robot rigidity or raising motor output, but by enhancing and reconfiguring the robot control technology. This shortens the time and increases the transportability in each process while maintaining a compact and slim design, while also improving assembly precision. This technology could only be developed by Epson, because it has both advanced robot technologies, and sensing technologies cultivated from the company's experience in developing a wide range of sensors.
In the future, Epson will continue to reduce process times by reducing robot vibration while increasing speeds and keeping down costs, and will develop products that combine sensor technologies and robot control. In this way, Epson will help improve the productivity of manufacturing worksites.