JPH0823502B2 - Position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a position detecting device used for detecting an absolute position of an arm, a work or the like in a robot, NC (numerical control device) or the like.

B. Outline of the Invention The present invention is a position detection device for detecting the absolute position of an arm, a work, etc. in a robot, NC, etc., combining an absolute encoder and a pulse generator, and using a pulse train of the pulse generator with an up-down counter. By increasing the LSB resolution of the absolute position data of the absolute encoder by counting, the total resolution can be improved by sharing the role of improving the resolution of the pulse generator even when using a low-cost absolute encoder. It was made possible.

C. Conventional technology In industrial robots, NC, etc., a pulse generator (PG) for position detection or an absolute encoder is used to detect the absolute position of the arm, work, etc.

The former is to count the pulse train, and the relative position from the count value at a specific arm position is used as a reference.

On the other hand, the latter is directly connected to the arm rotation shaft and can detect the absolute position.

D. Problems to be Solved by the Invention However, the former requires not only the origin search for starting the power supply of the apparatus but also the origin limit switch and the origin pulse.

In addition, the latter has a limit in principle for achieving high resolution, and also has a drawback that it is expensive.

The pulse generator is superior to the latter (absolute encoder) in terms of resolution and price. Conversely, in the case of an absolute encoder, the origin search
The advantage is that the origin limit switch and origin pulse are unnecessary.

D. Means for Solving the Problems The present invention is to attach an absolute encoder to an arm shaft in a robot or NC connected to a rotation shaft of a motor through a transmission mechanism of a required rotation ratio, and install an absolute encoder. In a position detection device that detects the absolute position of a pulse generator, etc., a pulse generator is attached to the rotary shaft of the motor, and while the pulse train is counted by an up-down counter, the least significant bit (LSB) of the absolute position data of the absolute encoder (LSB) is detected. ) Is provided with a circuit for detecting the leading and trailing edges of the pulse, and the up-down counter is reset at each detection time,
It is characterized in that the resolution of absolute position data is increased by the data of the up-down counter.

F. Action The pulse train of the pulse generator joins the up-down counter and is counted here. In this case, a reset pulse is added to the counter at every rising and falling edge of the least significant bit (LSB) of absolute position data. The data of the up-down counter is used for absolute position detection. As a result, the total resolution is increased and the absolute position can be accurately detected.

G. Embodiment FIGS. 1 to 3 show an embodiment of the present invention. FIG. 1 is a configuration diagram, FIG. 2 is a circuit diagram, and FIG. 3 is a time chart.

In FIG. 1, 1 is an arm, 2 is a motor, 3 is a transmission mechanism for transmitting the rotational force of the motor 2 to the shaft of the arm 1, and the rotation ratio thereof is 1: M. A pulse generator 4 is connected to the rotary shaft of the motor 2 and generates P pulses per revolution. An absolute encoder 5 is attached to the shaft of the arm 1 and has an N-bit resolution.

On the other hand, in FIG. 2, 6 is an up-down counter,
Reference numeral 7 is a CPU, and 8 is a pulse front / rear edge detection circuit for detecting the pulse rise and fall of the absolute position data D ₁ of the encoder 5. The counter 6 is, for example, 4 bits, and the output pulse train of the pulse generator 4 is added thereto, and the count result is sent to the CPU 7. The output of the pulse front and rear edge detection circuit 8 is applied to the reset input terminal RS of the counter 6. Also, the CP
The U7 so that addition of the most significant bit (MSB) of the absolute position data D ₁ to D _N from the encoder 5.

Next, the operation will be described. The required resolution is N +
Assuming K bits, N bits are discriminated by the absolute encoder 5 and the remaining K bits (4 bits in the embodiment).
Is discriminated by the pulse train of the pulse generator 4 being counted by the up-down counter 6. However,
The resolution of the pulse generator 4 is at least 2 ^K-1 times the bit of D ₁ of the absolute encoder 5.

That is, while the pulse train is input from the pulse generator 4 to the up-down counter 6, the output data of the absolute encoder 5 (the most significant bit (MSB of D ₁ , ..., D _N-1 , D _N in FIG. 3) (MSB )) Is input to CPU7. At this time, the data D ₁ is also input to the detection circuit 8 and its pulse falling edge and rising edge are detected. A reset pulse is added to the up-down counter 6 at each detection time. The data Q _{A to} Q _D of the counter 6 are as shown in FIG.

Thus, D, which is the LSB of the absolute encoder 5
_By resetting the up-down counter 6 at the rising and falling edges of the _1- bit pulse, the resolution of the D ₁ -bit is improved. This role is played by the pulse generator 4.

When the power is turned on, the K-bit (up-down counter value), which is the lowest bit, becomes indefinite. Therefore, in order to reset this and obtain the absolute position, the angle corresponding to 1/2 of the D ₁ bit, that is, the motor Motor 2 for 2 ^K-1 pulses on the axis
It is necessary to rotate the. However, this is actually an extremely minute rotation and can be performed in a short time, and in fact, the absolute position is detected. Also, the total resolution is 2 ^{N + K} bits, and the rotation ratio of the transmission mechanism 3 (1:
Considering M), Becomes Therefore, the encoder 5 should have a low resolution (low cost), and the resolution of the pulse generator 4 should be selected accordingly.

H. Effect of the Invention As described above, according to the present invention, an absolute encoder and a pulse generator are used, and a pulse train of this pulse generator is counted by an up-down counter to improve the resolution. Even if the absolute encoder is used, the total resolution can be improved and the cost can be reduced. Further, since the origin limit switch and the origin pulse of the pulse generator are not required, the configuration and the circuit are simple. Further, since the position can be detected by the axis of the arm, it is not necessary to increase the precision of the transmission mechanism between the motor and the arm so much, and there is an advantage that the manufacturing becomes easy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the position detecting device according to the present invention, FIG. 2 is a circuit diagram of the embodiment, and FIG. 3 is a time chart for explaining the operation. 1 ... Arm, 2 ... Motor, 3 ... Transmission mechanism, 4 ...
Pulse generator, 5 ... Absolute encoder, 6 ... Up-down counter, 7 ... CPU, 8 ...
Pulse front and rear edge detection circuit.

Claims (1)

[Claims] 1. A position detecting device for detecting an absolute position of an arm, a work or the like by attaching an absolute encoder to an arm shaft of a robot or NC which is connected to a rotation shaft of a motor through a transmission mechanism of a required rotation ratio. , Attaching a pulse generator to the rotary shaft of the motor,
The pulse train is counted by the up / down counter and the count result is supplied to the CPU, while the least significant bit (LS) of the absolute position data of the absolute encoder is
A position detecting device characterized in that a circuit for detecting the front and rear edges of the pulse of B) is provided, and the up-down counter is reset for each front and rear edge of the pulse detected by the detection circuit.