JPS6161053B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that generates displacement in response to an applied external force.

Conventionally, as an example of a device for converting this external force into displacement, there have been many devices that combine an elastic body 1 and a position detector 2 as shown in FIG. 1 is, for example, a spring, and 2 is, for example, a differential transformer. When the iron piece 2A of the differential transformer is displaced in response to the external force F to the position where the spring 1 and the external force F are approximately equal, the iron piece 2A
The change in position is extracted from the coil 2B of the differential transformer 2 as a signal. This type of conventional device is widely used, for example, as a tracer head for a type of scale or a tracing control device, but because it relies on an elastic body such as a spring for displacement, it has the following major drawbacks. There is. (1) The natural frequency of vibration is low because the ratio between the elastic force and the mass moved by the elastic body (hereinafter referred to as the torque-to-inertia ratio) cannot be large. (2) The braking action is weak. As a result, taking the tracer head as an example, its natural frequency is around 20 Hz, and it is easily affected by external vibrations associated with cutting of the machine during scanning control. On the other hand, there is an increasing need for this type of device to accurately convert even a small external force into displacement, and there is a great need to increase the so-called sensitivity of the tracer head. Weakening leads to a decrease in the natural frequency, making it increasingly susceptible to external vibrations.
Due to this restriction, it is currently not possible to reduce the contact pressure of the stylus attached to the tip of the tracer head very much.

There are also methods to achieve braking action, such as placing a brake piece directly connected to an elastic body in a dart pot or viscous liquid tank and utilizing the viscosity of the liquid.
It has the drawbacks of being complicated, expensive, and relatively susceptible to environmental conditions such as temperature and humidity.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a device for converting external forces into displacements which eliminates the drawbacks of the prior art.

By combining a force detector and a positioning servo system with a high loop gain, the device according to the present invention can perform critical damping or overbraking with respect to the vibration of the displaced part depending on the response characteristics of the servo system, while controlling the so-called sensitivity. This has the feature that the overall sensitivity can be greatly increased by increasing the gain of the signal from the force detector and applying it to the high loop gain servo system. As a result, when the device of the present invention is utilized in a tracer head, it is possible to realize a tracer head in which the vibration of the displacement part is brought to critical or over-damped mode, and the contact pressure of the stylus of the tracer head is significantly lower than that of the conventional tracer head.

Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 2 is a diagram showing the configuration of the first embodiment of the present invention. In FIG. 2, an external force F is applied to force detector 10. In FIG.

A first example of the force detector 10 is a piezoelectric detector in which electrodes are added to a crystalline lens as shown in FIG. As is well known, when a force is applied from a predetermined direction, the crystalline lens generates an electrical signal proportional to the force.
The crystalline lens 11 is subjected to an external force F sandwiched between insulators 14 and 15 via strong springs 12 and 13. Electric signals are transmitted from both sides of the crystalline lens 11 to resistors 16 and 17.
is applied to the differential amplifier 18 via. crystalline lens 1
A displacement of 1 is a negligible displacement on the order of several micrometers for an external force of several kilograms, and even if the external force F is small, an electrical signal with a sufficient S/N ratio can be extracted. A force detection signal 20 is thus obtained from the output terminal 19 of the amplifier 18. Normally, the natural frequency of such a crystalline lens is on the order of several MHz, which is a very high value with respect to mechanical vibrations. In addition,
Other piezoelectric elements with similar properties, such as ceramic piezoelectric elements, may be used instead of the crystalline lens described above. Another example of a force detector is shown in FIG. Fourth
In the figure, when an external force F is applied to an elastic body 21, a local portion thereof undergoes a minute displacement. In order to detect strain according to this displacement, strain gauges 22 and 23 are attached to the local areas, and these and resistors 24 and 2
5 and the power supply 26, and if the output of this circuit is applied to the amplifier circuit 27, a force detection signal 20 corresponding to the external force F is generated at the output terminal 28 of the circuit 27. The natural vibration frequency depends on the elastic force of the elastic body 21 and the mass of the vibrating part, but generally a fairly high natural frequency can be obtained.
Therefore, even if the damping effect of the elasticity itself is weak, the vibrations quickly converge.

Now, in FIG. 2, the force detection signal 20 is applied to a resistor 40 via a variable resistor 30. The force detector 10 is attached to a moving body 50. The moving body 50 is mechanically coupled to a motor 90 via a nut 60, a feed screw 70, and gears 80, 81. Further, a position detector 100 is attached to the movable body 50 to detect its position, and the terminal 10
1, a position detection signal 110 can be obtained. An example of the detector 100 includes a potentiometer slider 101, a potentiometer resistor 102, and a power source 103. As another example, a differential transformer or an optical scale may be used as the basic element. Motor 90 is driven by drive circuit 130. The circuit 130 includes, for example, an operational amplifier and a DC amplifier. The circuit 130 is connected to the position detection signal 110 via the resistor 120, as well as the variable resistor 30 and the resistor 4.
A force detection signal 201 that is fed back via a resistor 140 and an external equilibrium position command signal 150 of a moving body are applied via a resistor 140. In this case, since the position detection signal 110 is a feedback signal to the servo system, its polarity is the same as the equilibrium position command signal 15.
The polarity is opposite to 0. Further, the polarity of the force detection signal 20 is the same as the polarity of the equilibrium position command signal 150.

Now, when the external force F is not applied and the equilibrium position command signal 150 is applied from the outside, the circuit 130 rotates the motor 90 until the signal 150 and the signal 110 are balanced. Furthermore, the table 50 is moved via the nut 60 and the feed screw 70. The slider 101 moves relative to the resistor 102 as the table 50 moves, and this operation is performed until the signals 110 and 150 are balanced. In this state, external force F
When is applied to the force detector 10, a force detection signal 20 is generated, and the signal 20 is applied to the circuit 130 via the variable resistor 30 and the resistor 40. Since signal 20 was applied, circuit 130 outputs signal 150 and signal 2.
0 by the signal 110.
0, and the moving body 50 is eventually displaced to this point.

If the external force F fluctuates, the signal 1 will change depending on the value of the external force F.
The moving body 50 is displaced from the equilibrium position of the signal 10 and the signal 150. circuit 130, motor 90, moving body 50,
It is easy to see from the characteristics of the motor 90 and the circuit 130 that the positioning servo system including the position detector 100 can obtain a very high loop gain when the motor 90 is a DC motor and the circuit 130 is a DC amplification circuit. That's true. Moreover, in the present invention, even at such a high loop gain, a state of critical braking or overbraking can be obtained.
Therefore, the external force F applied to the servo system
Even if the value varies, the displacement operation of the table 50 will be an operation with good braking based on critical braking or over-braking of the servo system. In particular, the natural frequency of the force detector 10 is much higher than the response speed of the servo system, so even when the external force F fluctuates impulsively, the displacement operation of the servo system, that is, the table 50, is effective for braking. The behavior will be the same as before.

Next, the function of the variable resistor 30 will be explained with reference to FIG. Depending on the position of the slider of the variable resistor 30, the displacement of the moving body 50 with respect to the external force F can be varied in various ways. For example, when the slider of the resistor 30 is at the upper end, even if the external force F is small, the value of the signal 20 applied via the resistor 40 becomes large, and therefore the displacement of the moving body 50 is large. At this time, if compared to a normal spring, a soft spring system is realized. However, unlike a normal spring system, when the external force F is suddenly removed, the spring system has a small braking effect, so it vibrates around the equilibrium position many times. Moreover, as mentioned at the beginning of the description, a soft spring has the disadvantage that its natural frequency is very low. On the other hand, in this invention, if the external force F is suddenly removed, the force detector 10 itself may generate elastic vibrations with a very high natural frequency. Since the frequency is much lower than the frequency, the movable body 50 is displaced by the response speed and braking characteristics unique to this servo system until it reaches an equilibrium position when the external force is removed. Therefore, if this servo system is under critical braking or over-braking, unlike a normal spring system, it is possible for the movement to reach an equilibrium point and settle down without going too far.
Such a servo system can be easily realized.

Furthermore, even if the external force is large when the slider of the resistor 30 is located near the lower end, the resistor 40
The value of the signal 20 applied to the drive circuit 130 via is small. Therefore, the movement of the moving body 50 is small.
At this time, if we compare it to a normal spring, a rigid spring system is realized. However, what is different from a normal spring system is that the movable body 50 is displaced using the response speed and braking characteristics unique to the servo system, as described in the case of the soft spring system.

As described above, the present invention has the feature that the application ratio of the external force detection signal can be changed depending on the position of the slider of the variable resistor 30, and the ratio of the applied external force to the moving movement can be freely set. have.

Next, a resistor 140 connected to the drive circuit 130
Also, the function of the signal 150 added thereto will be described. By applying the equilibrium position signal 150 to the circuit 130 via the resistor 140, the equilibrium position of the mobile body 50 can be freely set. In terms of a spring system, this equilibrium position corresponds to the vibration equilibrium position that is normally mechanically adjusted manually. The present invention has a feature that it can be set using the signal 150 without any manual intervention. Therefore, when the commanded equilibrium position changes from time to time, the present invention
This is very convenient because no adjustment is required. In particular, changing the equilibrium position of the stylus in a tracer head of a tracing control device in which a stylus of a device as shown in FIG. 6 below is attached and the stylus is displaced in response to an external force applied to the stylus If signal 150
It has characteristics that can be easily realized by

FIG. 5 shows an embodiment in which the configuration shown in FIG. 2 is made practical. A moving body 250 in the figure corresponds to the moving body 50 in FIG. 2, and is supported by a frame 251 via a ball slide 243 and shafts 241 and 242. A force detector 210 is provided between the bolus slide 243 and the ball nut 244. When the external force F is applied to the moving body 250, the shafts 241 and 252 of the component force of the external force F
A force in the direction of acts on the force detector 210. The force detector 210 is supported by a ball nut 244, and the ball nut 244 is coupled to a motor 290 via a feed screw 270 and gears 280, 281. The potentiometer slider 201 is
Resistor 202 of potentiometer to moving body 250
are attached to the frame 251, respectively. Furthermore, although not shown in the figure, in addition to the ones already mentioned in the explanation of FIG. A resistor for the connected position detection signal, a resistor for the force detection signal,
There are resistors for command equilibrium position signals, etc.

FIG. 6 shows a plurality of units (element 30) of the embodiment shown in FIG.
0,400,500, etc.) and is attached to a frame 600. and applied external force F
This is an example in which the equation is decomposed into component forces F ₃₀₀ , F _{400 , and F 500 of the elements 300, 400} , and ₅₀₀ in the direction of each moving body, and each moving body is displaced according to each component force. The direction of the combined displacement of these displacements follows the direction of the applied external force F, and the magnitude of the combined displacement corresponds to the applied external force. Therefore, an external force in any direction can be converted into a displacement according to a component force in a desired direction. It can be seen that by exploiting this feature, the apparatus of FIG. 6 with stylus 700 attached to element 500 provides a three-dimensional tracer head.

In addition, according to the device of the present invention, a weight scale can also be realized, for example, by using a load cell of a force detector. This scale also exhibits the good braking that is a feature of this invention.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a device for converting external force into displacement, which combines a conventional elastic body and a position detector;
Figure 2 shows the basic configuration of this invention, Figure 3 shows the basic configuration of this invention.
The figure shows an example of a force detector with a high natural frequency used in this invention, Figure 4 shows another example of a force detector used in this invention, and Figure 5 is similar to Figure 2. FIG. 6 is a diagram showing an example of mechanically combining the present invention shown in FIG. 6, in which a plurality of the devices shown in FIG. FIG. 3 is a diagram showing an example of application of the present invention to realize the magnitude of displacement.

Claims (1)

[Claims] 1. A moving body, a position detector that generates a position detection signal according to the position of this moving body, a motor that displaces the position of this moving body, and a drive circuit that drives this motor, and generates the position detection signal. A movable body positioning servo system configured to provide feedback to the drive circuit, and a force detector attached to the movable body to generate an external force detection signal in accordance with the external force applied, A device for converting an external force into a displacement, characterized in that the position of a moving body is displaced in accordance with the applied external force by supplying an external force detection signal to the servo system.