JPS62203203A - servo circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

TECHNICAL FIELD The present invention relates to a servo circuit for controlling the position and speed of an object moved by a drive system such as a motor.

FIG. 3 is an overall configuration diagram of a known position control system.

The motor and motion mechanism 40 includes a motor whose driving force changes depending on an electric current, a speed reducer, and a moving body that is a load.

This moving body is called a controlled object. The current position and speed of this object are measured by a position sensor 41 and a speed sensor 42. The position measurement value xm and velocity measurement value vm obtained here are input to the servo circuit 43.

A position command value xr is input to the servo circuit 43 from a computer 44 or the like.

The servo circuit 43 calculates the driving force command value f from Xm, vm, Xr, etc. The calculation method is to multiply the difference (xrxm) between the position command value Xr and the position measurement value Xm by a predetermined number, and also to multiply the speed measurement value vm by a predetermined number to find the sum of the two.

The drive command value f is amplified by an amplifier 45 and given to the motor.

The present invention relates to a servo circuit among such control systems.

b) Conventional technology A constant by which the difference in position is multiplied is called a position gain P.

A constant that multiplies speed is called speed gain D.

FIG. 4 shows a configuration diagram of a conventional servo circuit. This is the case for position control.

When the position command value xr is given as a digital value D
The /A converter 46 performs analog value number conversion.

This value is input to the adder circuit 48 via the scale adjustment circuit 47.

The position measurement value Xm passes through the position gain adjustment circuit 50, is multiplied by an appropriate position gain P, and is input to the addition circuit 48.

The speed measurement value vm is multiplied by a speed gain D in a speed gain adjustment circuit 49 and then inputted into an addition circuit 48 . The driving force command value f is output from the adding circuit 48.

This is amplified and becomes the motor current and voltage values, which determine the motor driving force.

(2) Problems to be Solved by the Invention In these servo circuits, the position gain P1 and the speed gain D are constants that are independent of position. This is suitable when the characteristics of the controlled object do not change depending on the position.

However, there are also cases where the characteristics of the controlled object change depending on the position.

For example, this is the case with a rank mechanism as shown in FIG.

A crank 5 is included in the drive system consisting of a motor and a reducer 51.
3 is installed. This moves in a circle around the center 52. A guide 54 is provided on a straight line passing through the center 52.

A connecting rod 55 is rotatably attached to the end of the crank 53 by a pin 57. The other end of the connecting rod 55 is adapted to move along the guide 54 by means of a pin 58. Object 56 is connected to connecting rod 55 at pin 58.

The object 56 reciprocates within the guide 54, but its inertia varies depending on the rotation angle θ of the (motor) reducer.

Near the position θ1, the inertia of the object 56 hardly acts.

In the vicinity of position θ2, the inertia of the object 56 acts largely.

In a servo system, whether the motion of a moving body is linear or rotational, the displacement value is called position. Position therefore includes both distance and rotation angle.

In a motion system where inertia changes depending on position, such as the crank mechanism shown in Figure 5, it is difficult to obtain good responsiveness over a wide position range using conventional servo circuits that maintain constant position gain and speed gain. It may happen.

In order to overcome these drawbacks, the following software servo has been proposed.

This is a software servo system that reads measured values of position and speed into a computer, and uses software processing to switch gains depending on the position and calculate driving force.

Since the gain is switched according to the position Xm, the motion mechanism whose characteristics change depending on the position can be controlled over a wide range.

However, since gain switching is performed by software, the calculation time becomes long, and therefore it is difficult to apply this method to controlled objects that respond quickly or change rapidly. Another problem was that it was expensive.

A first object of the present invention is to provide a servo circuit that can perform good control over a wide range even if the controlled object has characteristics that change depending on the position of the object.

A second object of the present invention is to provide a fast-response servo circuit that can be applied to controlled objects that change rapidly.

A third object of the present invention is to provide a servo circuit that is cheaper than a software servo system.

(4) Configuration The servo circuit of the present invention attempts to solve this problem by using a gain memory that uses a position as an address and stores a gain corresponding to the position, since the gain is switched depending on the position.

That is, the servo circuit of the present invention outputs the speed deviation, which is the difference between the speed command value and the measured speed value, multiplied by the speed gain D, or outputs the result obtained by multiplying the speed deviation, which is the difference between the speed command value and the measured speed value, or outputs the result obtained by multiplying the speed deviation, which is the difference between the speed command value and the measured position value. It outputs the sum of the deviation multiplied by the position gain P and the speed measurement value multiplied by the speed gain, and has a gain memory that refers to the position measurement value as an address, and the position gain At least one of P and speed gain D is provided by the output of the gain memory.

FIG. 1 is a configuration diagram showing an embodiment in which the present invention is applied to position control.

This is an example of using a position sensor (not shown) whose position measurement value Xm is obtained as a digital signal, and a speed sensor (not shown) whose velocity measurement value vm is obtained as an analog signal. For example, a position sensor such as a rotary encoder and a speed sensor such as a tacho generator may be used.

The main components of this circuit are a subtraction circuit 1, a gain memory 2
, an adder circuit 3, a D/A multiplier 4, a D/A multiplier 5, etc.

The subtraction circuit 1 calculates a position deviation δx=the difference between a position command value xr given from a computer or the like and a position measurement value Xm.
Calculate Xr Xm.

Gain memory 2 is a memory that stores position gain P1 and speed gain D. These are stored as a function of position X. Therefore, with the position as an address, the corresponding position gain P1 and speed gain D are stored at the location indicated by the address. This is a characteristic point of the present invention. As a function of the position X, the gain P (xi, D
(xl is determined in advance, and P(xl, Dlxl is stored at the location where the address is X.) When the position measurement value Xm is connected to the address input, without any conversion, Immediately gain Plxl, D(
xl is output. There is no time delay due to calculation when determining the gain.

) The enemy multiplier 4 calculates the product of the positional deviation δx and the positional gain P. In other words, Pδx is determined.

D/A multiplier 5 calculates the product of speed measurement value vm and speed gain D. In other words, find Dvm.

The adder circuit 3 calculates the driving force command value f by calculating the sum of the above two products.

f=pδx + D vm (1)
In this example, the position measurement value xm % position command value vm is given as an analog quantity. Further, the driving force command value f is output as an analog quantity.

For this reason, the adder circuit 3 is also an analog adder.

Explain the action.

The position command value Xr is given from outside the servo system, such as a computer. This is given as a digital signal and temporarily stored in register 6.

The position measurement value Xm is given as a digital quantity by a position measurement sensor or the like. Here, position includes both distance and rotation angle.

The position measurement value Xm is temporarily stored by a register 8.

The oscillator circuit 7 generates a sample timing pulse with an appropriate repetition period τ. A pulse every τ updates the stored value XrXm in register 6.8.

The subtraction circuit 1 calculates the difference (
xr Xm ), that is, the positional deviation δm is calculated.

Although this is a digital signal, it is converted into an analog signal by the D/A converter 9.

Since the position measurement value Xm specifies the address of the gain memory 2, the position gain P1 and speed gain D, which are determined in advance as the optimum value for the value of Xm, are stored in the gain memory 2.
is output as a digital signal.

The position gain P is multiplied by the position deviation δx in the ) value multiplier 4. In other words, P×δx is obtained. Since the position gain P is a digital quantity and the position deviation δx is an analog quantity, a D/A multiplier is used.

The product of the speed gain D and the speed measurement value vm is calculated by the calculator 5. Therefore, Dxvm is calculated. Since the velocity gain D is a digital quantity and the velocity measurement value vm is an analog quantity, a pseudo multiplier is used.

The D/A multiplier 4 outputs PaX as an analog signal, and the D/A multiplier 5 outputs Dvm as an analog signal.

The adder circuit 3 calculates the sum of both analog quantities and sets it as the driving force command value f. This value is temporarily held by the sample hold 10. f is output to the next-stage amplifier circuit and converted into driving force for the motor.

Such calculations are repeated for each sample timing pulse. The oscillation circuit 7 provides simultaneous operation of the register 6.8 and sample hold 10.

This includes gain memory 2, multipliers 4 and 5, and addition circuit 3.
In order to prevent unnecessary fluctuations in the output signal until it operates and outputs the correct result f,
s X1% f etc. are temporarily fixed.

However, these are not necessarily required. If the operation of the gain memory and the arithmetic circuit is sufficiently fast and the motion of the object to be controlled is sufficiently slow, it is not necessary to apply the sample timing pulse from the oscillation circuit 1.

In this way, the driving force specification value f=P(Xm)(Xr
vm (2) will be obtained.

The present invention can also be used in servo circuits for speed control.

FIG. 2 is a block diagram of a servo circuit according to the present invention for speed control.

The speed command value vr is given as a digital quantity from an external device such as a computer. This is temporarily held by register 16.

A position measurement value xm is provided as a digital quantity by a suitable sensor.

The speed measurement value vm is provided as an analog quantity by the speed sensor.

The oscillation circuit 17 generates a sample timing pulse with a period τ.

The speed command value vr is converted into an analog quantity by the D/A converter 19.

The subtraction circuit 11 calculates the difference (vr-vm) between the speed command value vy and the speed measurement value vm. This value is the speed deviation δv
That's what it means. This is required as an analog quantity.

Although the position measurement value Xm is not explicitly included in the calculation of the driving force command value f, it is necessary as a parameter for determining the gain.

The position measurement value Xm is temporarily held in a register 18 and applied to the address input of the gain memory 12. The gain memory stores speed gain D(xm) corresponding to address Xm. In this example, since the position measurement value and command value are not included in the calculation, the gain memory does not contain the position gain but only the velocity gain.

Gain memory 12 outputs a velocity gain D (xm) corresponding to a given position measurement value Xm.

The D/A multiplier 14 calculates the product D of the speed gain D (xm) which is a digital signal and the speed deviation δ■ which is an analog signal.
Calculate (xm)δr.

This value is temporarily held in the sample hold 20 and output as the driving force command value f.

f = D (xm) δv (3) It is.

The oscillation circuit 17, register 16, register 18, and sample hold 20 have the same functions as in the example of FIG. If the values such as Xms vffl may change during these calculations, these values are temporarily fixed. If,
If the speed of the gain memory and arithmetic circuit is sufficiently faster than that of the controlled object, the sample timing pulse, the oscillation circuit 17, etc. are unnecessary.

As the gain memories IJ 2 and 12, it is easy to use a read-only memory (ROM) in which data has been written in advance. In this case, the relationship of gain to position measurements remains unchanged.

If the relationship of gain to position measurements is not constant, use a rewritable memo IJ RAM. An interface circuit for rewriting the contents of the RAM from the computer is provided, so that the computer can change the relationship between the gain and the position measurement value depending on the purpose.

In the servo circuit described above, the speed gain D1 and the position gain P are functions of the position measurement value of the controlled object itself, and this is used as the address.

However, it is not limited to this. There are cases where the movement of the controlled object is affected by other related drive systems. In such a case, the position measurement value x2 of the other drive system
, X3,..., speed gain D (Xt, X
2,..., xn) and position gain P (xl, x
2, ..., xn) are determined in advance. Then, the addresses are given by xl, x2, . . . xn.

Even if the characteristics of the control system vary greatly depending on the position of the controlled object, it is possible to construct a control system that exhibits good response at all positions.

By using the position measurement value as an address, the corresponding gain can be quickly read out from the gain memory.

Even objects that change rapidly can be controlled well.

The arithmetic circuit can be constructed using inexpensive elements. Moreover, the load on the host computer does not increase.

The host computer can manage many drive systems. As a result, the entire system can be constructed at low cost.

g) Applications Can be used to control industrial robots and various automatic machines.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of the present invention applied to position control. FIG. 2 is a configuration diagram showing an example of the present invention applied to speed control. FIG. 3 is an overall configuration diagram of a known position control system. FIG. 4 is a configuration diagram of a conventional servo circuit for position control. FIG. 5 is a diagram showing an example of a controlled object whose characteristics change depending on the position. 1... Subtraction circuit 2... Gain memory 3... Addition circuit 4... D/A multiplier 5... D/A multiplication Device 6.8...Register 7...Oscillation circuit 9...D/A converter 10...Sample hold 11...Subtraction circuit 12... Gain memory 14... D/A multiplier 16... Register 17... Oscillation circuit 18... Register 19... ... D/A converter 20 ... Sample hold Inventor Akihiro Ooka Kenji Okamoto 1) Yasushi

Claims (1)

[Claims] Position measurement value x_m and velocity measurement value v_m of the controlled object,
In a servo circuit that determines and outputs the driving force for driving the controlled object from the position command value x_r or the speed command value v_r, a speed gain D is added to the speed deviation δ_v, which is the difference between the speed command value v_r and the speed measurement value v_m. The output is the product of the position deviation δ_x, which is the difference between the position command value x_r and the measured position value x_m (x_r - x_m), multiplied by the position gain P, and the speed measurement value v_m is multiplied by the speed gain. It outputs the sum of the product multiplied by D,
It has a gain memory in which the gain for the position measurement value is determined in advance and the gain corresponding to the corresponding location is written using the position measurement value as an address. By giving the position measurement value as an address, the position gain P and the velocity gain D can be set. A servo circuit characterized in that at least one of the above is given as an output of the gain memory.