JP2006029366A - Position control method and apparatus for hydraulic closed circuit - Google Patents

Abstract

A position control method and apparatus for a closed hydraulic circuit that improves the position control by controlling the thrust and speed of a single rod cylinder and the displacement position of a rod of the single rod cylinder.
Pressure sensors (45, 46) are connected to pressure chambers (32, 36) on the head side and rod side of a cylinder (31), and the pressure chambers (32, 36) are connected to a hydraulic pump (35) integrated with a servo motor (47). ing. A load load 41 is urged to the piston rod 40, and a position sensor 48 that detects the displacement position of the rod 40 is provided in the vicinity of the tip of the piston rod 40. The outputs of the pressure sensors 45 and 46 are input to the thrust detection circuit 52 and input to the arithmetic circuit 55 from the own weight correction circuit 56. The output of the position sensor 48 is input from the position deviation detection circuit 54 to the position deviation-thrust conversion circuit 55. The output value calculated by the position deviation-thrust conversion circuit 55 is input from the cylinder area correction circuit 57 to the servo amplifier 50, and the servo motor 47 is controlled.
[Selection] Figure 1

Description

  The present invention relates to a position control method and apparatus for forming a closed circuit by a hydraulic pump and an actuator driven by an electric servo motor.

Conventionally, as this type of position control device for a hydraulic closed circuit, one using a hydraulic pump 102 driven by an electric servo motor 1 and a hydraulic cylinder 100 is known (see, for example, Patent Document 1).
Further, the position counter 79 indicating the position feedback value from the position sensor and the deviation of the position command value from the position command unit 71 are changed according to the values of the oil temperature sensor 19 and the pressure sensor 20 depending on the hydraulic oil temperature and pressure, and the hydraulic pressure Some servo amplifiers 43 are given to the servo amplifier 43 as a rotation command for the servo motor 43 after correcting for internal leakage from the device (see, for example, Patent Document 2).
In Patent Documents 1 and 2, the suction side flow rate and the discharge side flow rate of the pumps 100 and 35 are the same. On the other hand, since the hydraulic cylinders 100 and 13L (13R) are single rod cylinders, the volume change on the rod side of the hydraulic cylinders 100 and 13L (13R) differs from the volume change on the head side with respect to the movement amount of the piston. In addition, pilot check valves 110 and 112 and a shuttle valve 61 are used as intake valves that compensate for the shortage of hydraulic fluid on the head side when the rod extends. Furthermore, when the rod moves backward, excess hydraulic oil on the rod side is returned to the tank.

On the other hand, the problem of the hydraulic closed circuit using a single rod cylinder, for example, hydraulic oil that transmits driving force and drag, is supplied to the rod side and the head side chamber of the actuator 4 by the servo motor 10a, the hydraulic pump 20a, and the servo motor 10b, respectively. When the hydraulic pump 20b is connected and the actuator 4 is driven, the hydraulic oil that transmits the driving force and the drag is heated by the action of the servo motor 10a, the hydraulic pump 20a and the servo motor 10b, and the hydraulic pump 20b. (For example, refer to Patent Document 3).
Japanese Patent Laid-Open No. 10-78003 JP 2001-205342 A JP 2001-90704 A

  However, in the hydraulic closed circuit of the single rod cylinder using the pilot check valve and shuttle valve described in Patent Documents 1 and 2, a large drag proportional to the speed, that is, the generation of viscous resistance cannot be expected, and the load weight is If it is large, there is a problem that the single rod cylinder tends to oscillate. In order to avoid these oscillations, a fixed throttle or variable throttle is provided at the outlet of the cylinder head side and rod side pressure chamber in the previous hydraulic closed circuit. Heat is generated in proportion to the product of the differential pressures, and wasteful energy is consumed, and the tank capacity needs to be increased for heat dissipation.

In Patent Document 3, since the servo motors 10a and 10b, the controller 11, and the hydraulic pumps 20a and 20b are used, the apparatus becomes large, and the compactness that is an advantage of the closed circuit is lost. Further, when the drag generating pump operates as a motor, the servo motor is rotated from the shaft side, and when it functions as a generator, the generated power is often consumed by regenerative resistance. For this reason, even if the oil temperature of the hydraulic oil does not rise, the energy generated as a drag becomes heat, so that the energy saving effect by the closed circuit using the servo motor is reduced.
The present invention has been made to solve the above problems, and in a closed hydraulic circuit comprising a hydraulic pump driven by an electric motor and a single rod cylinder, the thrust and speed of the single rod cylinder and the rod of the single rod cylinder It is an object of the present invention to provide a method and an apparatus for controlling a closed hydraulic circuit in which the displacement position of the single rod cylinder is controlled to improve the position control performance.

In order to achieve the above object, the present invention provides a hydraulic cylinder position control method in which a servo motor operates a hydraulic pump and is operated by hydraulic oil supplied from the hydraulic pump.
The servo motor is rotated based on a position command, and an output value from a position sensor for detecting the position of the hydraulic cylinder is fed back to obtain a position deviation of the hydraulic cylinder obtained in advance with respect to the output value. The output value from the pressure sensor that detects the pressure in the head side and rod side pressure chambers of the hydraulic cylinder is fed back and converted into thrust, and the thrust command proportional to the position deviation is used as the rotation command to the servo motor. It is characterized by being granted.
Next, the present invention provides a hydraulic cylinder position control device in which a servo motor operates a hydraulic pump and is operated by hydraulic oil supplied from the hydraulic pump.
A position sensor for feeding back an output value obtained by detecting the position of the cylinder;
A position deviation detection circuit for obtaining a position deviation of the output value of the position sensor from a position command value of the cylinder obtained in advance;
A thrust detection circuit that feeds back the output of the cylinder head side and rod side pressure chambers and converts them into thrust,
A pressure receiving area correction circuit for correcting the thrust to the same output value regardless of the pressure receiving area difference by means such as multiplying the feedback value of the rod side pressure chamber by a value obtained by dividing the rod side pressure receiving area by the head side pressure receiving area;
A self-weight correction circuit that calculates the thrust corrected by the thrust detection circuit to a thrust corresponding to the load acting on the hydraulic cylinder, and corrects the output in a state where only the self-weight is biased to zero;
A position deviation-thrust conversion circuit for calculating a difference between the position deviation and the thrust corrected for its own weight;
It is characterized by comprising.
According to the present invention, by giving the deviation between the position deviation and the thrust as a rotation speed command to the servo motor, hunting and abnormal vibration can be prevented, and the closed loop gain can be increased by 5 times or more. Thereby, the positioning accuracy of several μm can be ensured even under the condition that the positioning accuracy is conventionally several tens of μm.
In this case, even if there is no movement of the load, the rotation command to the servo motor can be suppressed when a necessary and sufficient thrust is generated, so that it is possible to suppress useless jumping of the load.

  In the present invention, by giving a deviation between the position deviation and the thrust as a rotation speed command to the servo motor, hunting and abnormal vibration can be prevented, and the closed loop gain can be increased by 5 times or more. As a result, the positioning accuracy of several μm can be ensured even under the condition that the positioning accuracy is conventionally several tens of μm.

A hydraulic closed circuit control device 30 according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a hydraulic closed circuit control device 30 (hereinafter abbreviated as control device 30) according to an embodiment of the present invention.
As shown in FIG. 1, the head-side pressure chamber 32 of the cylinder 31 is connected to one side of a hydraulic pump 35 by pipe lines 33 and 34, and the rod-side pressure chamber 36 is a hydraulic pump by pipe lines 37 and 38. 35 is connected to the other side. A load 41 is provided at the tip of the piston rod 40 that moves in the directions of the arrows X and Y. Note that. The head side pressure chamber 32 is formed to have a larger pressure receiving area than the rod side pressure chamber 36.

  The pipe lines 33, 34 and 37, 38 are connected via a pipe line 42. The pipe line 42 is provided with check valves 43, 44 for flowing hydraulic oil in one direction, and a head side pressure chamber. 32, a head side pressure sensor 45 for detecting the pressure of the hydraulic oil acting on the rod side pressure chamber 36, and a rod side pressure sensor 46 are provided. A position sensor 48 for detecting the displacement position of the piston rod 40 is provided in the vicinity of the tip of the piston rod 40. The servo motor 47 is connected integrally with the hydraulic pump 35 and is connected to the servo amplifier 50 by a cable 49.

A detection signal from the head-side pressure sensor 45 is converted into a voltage value and input to a thrust detection circuit 52 that detects a thrust generated in the head-side pressure chamber 32 or the rod-side pressure chamber 36. A detection signal from the rod side pressure sensor 46 is also converted into a voltage value, and is input to a thrust detection circuit 52 that detects a thrust from a pressure receiving area correction circuit 51 that corrects a pressure receiving area difference between the head side pressure chamber 32 and the rod side pressure chamber 36. Is done. Further, a detection signal from the position sensor 48 is input to the position deviation detection circuit 53.
In the pressure receiving area correction circuit 51, the pressure in the head side pressure chamber 32 is multiplied by K1 = (pressure receiving area B of the rod side pressure chamber 36 ÷ pressure receiving area A of the head side pressure chamber 32), and is the same regardless of the pressure receiving area difference. It has a function of converting the output value to the same thrust value. K1 represents a constant.

An output obtained by detecting the position of the piston rod 40 by the position sensor 48 and a position command value 53 sent from a command device (not shown) are sent to the position deviation detection circuit 54, and the position deviation between the output value of the position sensor 48 and the position command value 53 is sent. Is transmitted to the position deviation-thrust conversion circuit 55.
The position deviation detection circuit 54 compares the position finger value 53 indicated by the position command with the current value indicated by the position sensor 48, and transmits an output value compared with the error. Has the function to show.
The position deviation-thrust conversion circuit 55 operates in the same manner as a normal operational amplifier. For example, when the position deviation is −1 mm, the pressure between the pressure in the head-side pressure chamber 32 and the pressure in the head-side pressure chamber 36. When the difference is 20 MPa, the output is set to zero, and when the positional deviation is +1 mm, the pressure difference between the pressure in the head side pressure chamber 32 and the pressure in the head side pressure chamber is -20 MPa and the output is set to zero.
If the gain of the position deviation-thrust conversion circuit 55 is set to zero, a circuit that gives a rotational speed command proportional to the position deviation to the servo motor 47 via the servo amplifier 50 can be obtained.

  Further, the thrust in the head side pressure chamber 32 or the rod side pressure chamber input to the thrust detection circuit 52 is sent to the position deviation-thrust conversion circuit 55 via the self-weight correction circuit 56. The self-weight correction circuit 56 corrects the thrust corresponding to the self-weight when the load 41 urged by the piston rod 40 of the cylinder 31 acts in the arrow Y direction (upward) or the arrow X direction (downward). , Having a function as a voltage shift circuit for correcting the output of the self-weight correction circuit 56 in a state where the self-weight is energized to zero.

The control device 30 according to the embodiment of the present invention is basically configured as described above, and the operation thereof will be described next.
First, when the piston rod 40 of the cylinder 31 is displaced in the direction of the arrow X, for example, a load 41 is urged to the piston rod 40. At this time, the output detected by the position sensor 48 and the position command value 53 of the position command are input to the position deviation detection circuit 54.
On the other hand, the pressure in the head-side pressure chamber 32 of the cylinder 31 is converted into a voltage value by the head-side pressure sensor 45 and input to the thrust detection circuit 52. The pressure in the head-side pressure chamber 32 is corrected to the same thrust with the same output value by the pressure receiving area correction circuit 51 regardless of the pressure receiving area difference, and is input to the thrust detection circuit 52 to the actually generated thrust value. It is converted and input to its own weight correction circuit 56.

  Then, the output of the position deviation detection circuit 54 and the output of the self-weight correction circuit 56 are input to the position deviation-thrust conversion circuit 55, and the servo amplifier 50 uses the voltage converted so that the thrust after the self-weight correction is proportional to the position deviation. , The rotational speed of the servo motor 47 is controlled, and the position of the cylinder 31 is controlled by controlling the thrust.

It is a block diagram of the position control apparatus of the hydraulic closed circuit which concerns on embodiment of this invention.

Explanation of symbols

30 Position Control Device for Hydraulic Closed Circuit 31 Cylinder 35 Hydraulic Pump 44, 45 Pressure Sensor 47 Servo Motor 48 Position Sensor 50 Servo Amplifier 51 Pressure-Receiving Area Correction Circuit 52 Thrust Detection Circuit 53 Position Command Value 54 Position Deviation Detection Circuit 55 Position Deviation-Thrust Conversion circuit 56 Weight correction circuit

Claims (2)

In a hydraulic cylinder position control method in which a servo motor operates a hydraulic pump and is operated by hydraulic fluid supplied from the hydraulic pump,
The servo motor is rotated based on a position command, and an output value from a position sensor for detecting the position of the hydraulic cylinder is fed back to obtain a position deviation of the hydraulic cylinder obtained in advance with respect to the output value. The output value from the pressure sensor that detects the pressure in the head side and rod side pressure chambers of the hydraulic cylinder is fed back and converted into thrust, and the thrust command proportional to the position deviation is used as the rotation command to the servo motor. A method for controlling a hydraulic closed circuit, characterized by being provided. In a hydraulic cylinder position control device in which a servo motor operates a hydraulic pump and is operated by hydraulic oil supplied from the hydraulic pump,
A position sensor for feeding back an output value obtained by detecting the position of the cylinder;
A position deviation detection circuit for obtaining a position deviation of the output value of the position sensor from a position command value of the cylinder obtained in advance;
A thrust detection circuit that feeds back the output of the cylinder head side and rod side pressure chambers and converts them into thrust,
A pressure receiving area correction circuit for correcting the thrust to the same output value regardless of the pressure receiving area difference by means such as multiplying the feedback value of the rod side pressure chamber by a value obtained by dividing the rod side pressure receiving area by the head side pressure receiving area;
A self-weight correction circuit that calculates the thrust corrected by the thrust detection circuit to a thrust corresponding to the load acting on the hydraulic cylinder, and corrects the output in a state where only the self-weight is biased to zero;
A position deviation-thrust conversion circuit for calculating a difference between the position deviation and the thrust corrected for its own weight;
A position control device for a hydraulic closed circuit, comprising:

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