JPS6317726B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed control device for a conveying device that performs highly accurate positioning at a target position.

Conventionally, conveyance devices that require high-precision positioning have been equipped with mechanical mechanisms such as stoppers,
On top of that, devices have been used in which positioning is performed by inserting a dowel pin into a positioning hole previously provided in the carrier. In order to keep the impact within a small range, such methods have drawbacks such as the inability to increase the weight to be transported and the inability to increase the transport speed.

Furthermore, a method in which positioning is performed by pure control such as a speed control device or a servo mechanism is also often used. However, conventional systems require a highly accurate position detector and are expensive, making them unsuitable for use in large-scale conveyance systems.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide a conveying device that is equipped with an inexpensive speed target setting device and is capable of large-scale, high-speed conveyance.

In order to achieve the above object, the main points of the present invention are to create a relatively rough step-like target speed curve in areas far from the stop target, and to create a target speed curve that continuously changes only in areas close to the stop target. do.

The present invention will be specifically described below based on embodiments shown in the drawings.

FIG. 1 shows an example of a conveying device to which the present invention is applied, in which 1 is an excitation coil of a linear motor fixedly installed on a ground surface 3, and 2 is a pallet traveling on a surface 4. The pallet 2 also serves as a secondary conductor of the linear motor. Further, a support device for the pallet 2 is not shown. In this figure, the pallet 2 approaches the excitation coil 1 from a distance and is controlled so as to stop when the center _O2 of the pallet 2 coincides with the center _O1 of the excitation coil 1. After this,
After a predetermined period of time, the pallet 2 leaves the O ₁ position again and travels toward the next target. When performing such an operation, it is necessary to accurately stop the pallet center _O2 at the stop position _O1 . Particularly when such a device is used on a production assembly line, such positioning control requires special precision.

FIG. 2 shows the characteristics of a speed target often used for high-precision positioning. This characteristic relates to the position of O ₂ with respect to the stop target O ₁ , and it is desirable that the zero line intersects at the position of O ₁ , and that the deceleration section before and after that becomes a straight line without unevenness.

However, if the entire deceleration section is to be made straight, expensive equipment will be required.

FIGS. 3 and 4 are diagrams showing an embodiment of the present invention that solves such problems. What is shown in Fig. 3 shows the position detection method, in which 21 is the object to be detected mounted on the pallet, the upper surface of which is a smooth straight line;
The bottom surface has equally spaced notches.
On the other hand, A ₃ and B ₃ are fixedly arranged symmetrically around the stop target O ₁ , output when the top surface of the object to be detected approaches, and perform gap detection where the output changes depending on the approach. It is a vessel. On the other hand, A ₂ and A ₃ are also fixedly arranged symmetrically around the stop target O ₁ ,
This is a proximity switch that detects a notch on the underside of an object to be detected. The outputs of the proximity switches A ₂ and B ₂ have an on-off shape that corresponds precisely to the shape of the notch in the object 21 to be detected. A ₁ and B ₁ are proximity switches similar to A ₂ and B ₂ , but the fixed positions are slightly shifted.
This is used to identify the direction of pallet movement. On the other hand, what is shown in FIG. 4 shows the actual configuration of the apparatus of the present invention. In the figure, 1 is an excitation coil of a linear motor, which is controlled by a speed control device 5. Reference numeral 6 denotes a subtracter which provides a control input to the speed control device 5 and determines its output by subtracting the output of the adder 7 and the output of the speed detector 13. In such a configuration, the output of the subtracter 6 is usually used as the speed deviation, and the output of the adder 7 as the speed deviation.
The input from the speed detector 13 is called a speed target value, the input from the speed detector 13 is called a speed feedback input, etc., and it can be understood that a speed control system is constructed. 8 is a maximum value detector, 9 is a minimum value detector, 10 is a polarity inverter, 11
is a position-to-speed target value converter, 12 is a position detector,
14 is an OR element, A ₂ and B ₂ are the proximity switches, and A ₃ and B ₃ are the gap detectors.

FIG. 5 is an explanatory diagram of the operation of such an apparatus of the present invention. That is, the proximity switches A ₂ and _{B 2} respectively generate an on-off signal a shown in FIG. 5A and an on-off signal c shown in FIG. occurs. On the other hand, gap detectors A ₃ and B ₃ generate a signal b shown in FIG. 5B and a signal d shown in FIG. 5D depending on the proximity of the upper surface of the detected object 21. It is clear from the relative positional relationship between the detected object 21 and the gap detectors A ₃ and B _{3 that the signals b and d switch so as to intersect at the point where the pallet center O 1 coincides} with the exciting coil center position O ₂ . Probably. OR element 1
By performing the logical sum of signals a and c using 4, a signal e shown in FIG. 5E is obtained. The position detector 12 receives the signal e
As a result, a stepwise signal f shown in FIG. 5F is generated. Although the internal circuit of the position detector 12 and the mechanism for generating the signal f will not be described in detail, a circuit having such characteristics can be constructed by combining a so-called preset counter and a digital-to-analog converter. The output of the polarity inverter 10 generates a signal g shown in FIG. 5G by inverting the polarity of the signal d. Maximum value detector 8 generates signal h ₃ from signals b and f. The minimum value detector 9 detects the signal from the signals g and f.
Generate h ₄ . As a result, adder 7 receives signals h ₃ and h ₄
Add to create signal _h5 . Signal _h5 is the target value of the speed control system. This target value intersects the zero line at the point of stop target O ₂ . Therefore, it is possible to achieve high stopping accuracy. Further, the portion faster than the stop target O ₂ has a step-like shape, but as it approaches the target O ₂ it approaches zero, so it is suitable as a target value for stop control. In contrast, a speed target setting device such as that shown in FIGS. 3 and 4 is simple.

As described above, the present invention does not require a very expensive position detector, enables highly accurate positioning, and makes it easy to position large-scale conveyance equipment purely by control. It became.

Therefore, it is easy to increase the transport weight or increase the transport speed of a transport device that requires highly accurate positioning.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conveyance device to which the present invention is applied, FIG. 2 is a diagram showing typical speed target characteristics of a device that performs high-precision positioning, and FIGS. FIG. 5 is a diagram showing a signal waveform explaining the operation of the device of the embodiment. Explanation of symbols 1...Linear motor excitation coil, 2
... Secondary conductor, 3 ... Floor surface, 4 ... Running surface, 5 ... Speed control device, 6 ... Subtractor, 7 ... Adder, 8 ... Maximum value detector, 9 ... Minimum value detector, 10 ... Polarity inverter ,1
DESCRIPTION OF SYMBOLS 1...Position-to-speed target value converter, 12...Position detector, 13...Speed detector, 21...Detection object, _A1 , _B1 ,
A ₂ , B ₂ ... Proximity switch, A ₃ , B ₃ ... Gap detector.

Claims (1)

[Claims] 1. In a speed control device for a conveying device that performs high-precision positioning at a target position, there is provided a means for obtaining step-like target speeds of equal magnitude and opposite polarity around the target position, and a means for obtaining step-like target speeds of equal magnitude and opposite polarity in the vicinity of the target position. first continuously variable target speed means for obtaining a continuously variable target speed that changes in proportion to the positional deviation; and a continuously variable target speed that has a negative polarity near the target position and changes in proportion to the positional deviation. a maximum value detector for selecting the larger of the stepped target speed and the first continuously changed target speed; and a maximum value detector for selecting the larger of the stepped target speed and the first continuously changed target speed; The present invention is characterized by comprising a speed target setting device comprising a minimum value detector that selects the smaller one of the target speeds, and an adder that adds the signal of the maximum value detector and the signal of the minimum value detector. Speed control device for conveyor equipment.