Piezo Impact Drive Mechanism

Keywords: Impact Drive Mechanism, piezoelectric actuator, micro machine, micro actuator, precise positioning, friction force

Introduction

Impact Drive Mechanism (IDM) is a method for moving an object under friction by impulsive force. It utilizes static friction and impulsive force caused by the rapid displacement of an actuator. The motion mechanism basically consists of three parts: the main body, actuator and the inertial weight. When the actuator makes rapid extension or contraction, a strong inertial force is generated and the main body is moved against static friction. When the actuator makes slow retraction, the inertial force could be smaller than static friction so that the main body keeps the position. Repeating those fast and slow actuator displacements carries out the motion.

The mechanism is able to control the minute motion of several nanometer and at the same time has virtually unlimited movable range. The mechanism can be extended to multiple degree-of-freedom systems with multiple actuators and counter weights. The IDM is considered to be a suitable mechanism for micro systems since its construction is quite simple.

The mechanism generates impulsive force when moving. We have utilized such impulsive force to develope a printed board positioning device, a centering system for workpieces on rotating supports, and a piezo-electric maicro manipulator.

Operation Principle[1]

Figure 1 shows a basic motion principle of the Piezo Impact Drive Mechanism. The motion mechanism consists of three components: the main body, the actuator and the inertial (counter) weight. The main body is laid down on the guiding surface with only the friction acting between the surface. On the one end of the main body an actuator is attached. The weight does not touch the surface.

The processes of the motion are described as follows:
(a) The cycle starts with the actuator in extended state.
(b) The actuator makes slow contraction so that the inertial force caused by the contraction should not exceed the static friction. The main body keeps the position.
(c) At the end of contraction process, a sudden stop of the motion is made to small move the main body.
(d) Then, a rapid expansion of the actuator causes impulsive inertial force, which results in the step-like motion of the main body.
Making slow extension and rapid contraction can carry out motion toward the other direction. The motion amplitude of the actuator can control the step size of the motion. Repeating those processes through (a)-(d) a long distance motion is made possible.

Moving toward left Voltage waveforms Animation
(Moving toward left) (Voltage Waveforms)
Figure 1: Operation Principle

Motion characteristics

Figure 2 shows a linear motion device of Impact Drive Mechanism for basic experiments. Employed piezo-electric element has size of 10 x 10 x 20 [mm]. It generates 16µm displacement at 150V applied voltage.

Fig. 3 shows a nanometer-scale continuous step motion. The size of the steps is about 4nm. Controlling voltage amplitude applied to the piezoelectric actuator, nanometer motion can be controlled. The maximum load capacity of the Impact Drive Mechanism depends on the static friction. If the static friction is large enough, the Impact Drive Mechanism can climb up the vertical surface.

Basid 1-DOF setup
Figure 2: Basic 1-DOF setup
Motion
Figure 3: Motion of IDM (nano-meter motion)

Features

Some remarkable features are listed in the following.
  1. Simple structure
  2. Nano meter positioning, long movable range, and high-speed motion can be realized at the same time
  3. Ease of making multi degree of freedom mechanism(eg. figure 4)
  4. No energy requirement for keeping constant position
Multi-DOF mechanism
Figure 4: Multi-DOF mechanism

Applications

  1. Precise positioning stage
  2. 3-DOF ultrahigh vacuum stage[2]
  3. Micro robotic arm(Figure 5)[3]
  4. a centering system for workpieces on rotating supports
  5. Printed board position device[4]
  6. Piezo Micro Manipulator[5]
  7. Piezo Injector
Micro robotic arm
Figure 5: Micro robotic arm

References

[1] T.Higuchi, Y.Yamagata, K.Furutani, and K.Kudoh "Precise positioning mechanism utilizing rapid deformations of piezoelectric elements", Proc. of IEEE Workshop on Micro Electro Mechanical Systems, pp.47-51 (1990)

[2] Y.Yamagata, T.Higuchi, H.Saeki, and H.Ishimaru: "Ultrahigh Vacuum Precise Positioning Device Utilizing Rapid Deformations of Piezoelectric Elements", Journal of Vacuum Science and Technology, A, Vol. 8, No. 6 Nov./Dec., pp. 4098-4100 (1990)

[3] T.Higuchi, Y.Yamagata, K.Kudoh, K.Iwasaki: "Micro Robot Arm Utilizing Rapid Deformations of Piezoelectric Elements", Proc. 5th International Symposium on Robotics Research, The MIT Pres, Aug., pp. 441-445 (1989)

[4] Yutaka Yamagata and Toshiro Higuchi, "A Micropositioning Device for Precision Automatic Assembly using Impact Force of Piezoelectric Elements", Proceedings of the IEEE International Conference on Robotics and Automation, pp. 666-671 (1995)

[5] K.Kudoh,T.Goto,K.Sato,Y.Yamagata,K.Furutani,T.Higuchi "Development of Piezo Micromanipulator fr cell Micromanipulation" J.Mamm. Ova. Res. (Japanese), Vol.7, No.1, pp. 7-12 (1990)

Back
Higuchi Lab.