MMD-200

The Six-Dimensional Motion Measurement Device (MMD) is an innovative product of LEI & SO Co., Ltd. The MMD is designed to measure the motion of the tool relative to the workpiece on a machine in shop floor. The measured motion is six-dimensional, including three translations and three rotations.

Once the MMD is installed on a machine, it can be used for all kinds of measurements and inspections such as the calibration of DH kinematic parameters of an industrial robot, the calibration of link parameters of the two rotary axes of a five-axis machine tool, the tracking of dynamic motion errors and the measurement of thermal errors of a main spindle.

High rigidity optical scale ball bar

The three parallel rods of the readhead assembly and the scale assembly of the optical scale ball bar form a spatial structure with excellent rigidity against bending. Four parallel rods and bushes guide the readhead assembly and the scale assembly to perform highly accurate linear motion. The use of optical scale as displacement sensor has the advantages of high accuracy and large measuring stroke.

Thermally stable platforms

The upper and the lower platform both have multi-layer design. One low CTE layer is for the definition of ball joint position and another load bearing layer for the transport of the platform. Therefore, all ball joints on the upper and the lower platforms are thermally stable by large ambient temperature change. Besides, a transport of the platform does not affect the position of the ball joints on the platform.

Real-time thermal errors compensation

The MMD faces the challenge of maintaining its measurement accuracy under changing ambient temperature in shop floor up to 5℃. The patented method uses an extra ball bar, the reference ball bar RBB, for the thermal error compensation. The RBB is placed on two supports on a calibrator with near-zero CTE. Since the distance between the two supports is constant, the change of reading of the RBB reflects the effects of the changing ambient temperature on all working ball bars. The thermal errors of all working ball bars are measured by the RBB and compensated accurately.

Geometric errors measurement for machine tools

All MMD measured data are defined in a single reference coordinate system. A processing of the measured data can obtain the 21 geometric errors of a three-axis machine tool, the 8 link parameters of the two rotary axes of a five-axis machine tool, and the position and orientation of the main spindle.

Identifying kinematic parameters of a six-axis robotic arm

It is advantageous to use the MMD to identify the position and orientation of each joint axis in a robotic arm. By driving the joint motors one after another, the positions and orientations of all joint axes can be determined. The DH kinematic parameters can also be identified accurately using the data of all joint axes.

6D Circular tracking

In case the MMD is used for a circular tracking test, the measured results show not only the change of radius, but also the three translational and three rotational motion errors during the circular tracking.

Measurement of dynamic motion

The MMD can measure dynamic errors of any continuous or non-continuous motion such as overshot or oscillation. The path type for the dynamic motion test includes point-to-point, linear, circular, spline, NURBS and any combination of them.