JP2006112114A - Swing control device for construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a swing control system harmonizing speed control and torque control of a swing body well. <P>SOLUTION: A control means determines target speed and limit torque based on an operation signal of an operating means, obtains a torque value by feedback control from the deviation between the target speed and the swing speed of a speed detecting means, compares the torque value with the limit torque, and sets the torque value with a smaller absolute value as a torque control quantity to obtain a control input signal of an inverter together with the target speed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a turning control device for a construction machine that drives an upper turning body mounted on a lower traveling body by an electric motor.

  Conventionally, construction machines have adopted a hydraulic drive system in which a hydraulic pump is driven by an engine and an actuator is driven by oil discharged from the hydraulic pump. However, in the hydraulic drive system, a plurality of actuators are driven and controlled by pressure oil discharged from one hydraulic pump, and a high discharge pressure is set so that each of the plurality of actuators can be driven and controlled. Yes. Therefore, in the case of controlling an actuator that is operating only with a light load, there is still a problem that hydraulic energy is wasted because high-pressure return oil is still released to the oil tank.

Therefore, recently, an electric motor drive system using an electric motor as a drive source has been proposed. In the electric motor drive system, as disclosed in Patent Document 1, an inverter is connected to each electric motor to be used, and the inverter is controlled so as to be a power source suitable for the electric motor. Therefore, a low-output power source may be configured for an actuator that operates only with a light load, and a high-output power source may be configured for an actuator that operates with a heavy load. However, in the turning control of the upper turning body of construction machines such as hydraulic excavators, there are cases of light loads only for turning operations and cases of heavy loads that turn while pushing a bucket during excavation work. In order to maintain the same working feeling as the case, the speed control method is adopted for light loads and the torque control method is adopted for heavy loads. In order to automatically switch between these control methods, it is necessary to identify light load work and heavy load work.
JP 2003-82707 (electric construction machine and electric excavator)

Patent Document 2 (hereinafter, referred to as the conventional device 2) discloses a technique in which torque control is performed instead of feedback speed control during a pressing operation. According to this, the start position, the target value of the turning speed, and the torque target value are defined according to the operation amount of the operation lever, the actual value of the turning speed is detected, and the target value of the turning speed and the actual value of the turning speed are detected. And a feedback control (PID control) is performed. As a result, when the operation amount exceeds the movement start position and the actual value of the turning speed is smaller than the threshold value, it is determined that the pressing operation is performed, and the control method is switched, and torque control is performed based on the torque target value. The threshold value is set as a minute value close to zero.
JP 2003-328398 (turning control device for work machine)

  In the conventional device 2, torque control based on the torque target value is performed when the actual value of the turning speed is substantially zero, and feedback control is performed when the turning speed exceeds the threshold value. However, if feedback control is performed even when the turning speed slightly exceeds the threshold value, the control torque in this case may greatly exceed the torque target value, which not only makes it difficult to define the torque target value. In some cases, the regulation of the torque target value itself becomes meaningless, and there is a problem that the control becomes unstable.

Patent Document 3 (hereinafter referred to as the conventional device 3) also describes a control method using an electric motor drive system. According to this document (see FIG. 4 in particular), acceleration torque and braking torque in the case of torque control are defined according to the operation amount of the operation means. That is, the acceleration torque is zero in the section from the zero point of the manipulated variable to the rising point (S), the acceleration torque increases in the section beyond the rising point, and becomes the maximum acceleration torque in the subsequent final section. . On the other hand, the braking torque becomes the maximum braking torque in the first half region including when the operation amount is zero, and increases from zero to the maximum braking torque in accordance with the decrease in the operation amount when returning from the maximum operation amount to the intermediate position in the second half region. Is set to
Japanese Patent Application Laid-Open No. 2001-10784 (Swivel Control Device for Swivel Work Machine)

  In the conventional device 3, since the braking torque is smaller than the maximum braking torque when returning from the maximum operation amount to the intermediate position in the second half region of the operation amount, the braking torque is insufficient before returning to the intermediate position. As a result, controllability may deteriorate, which is a problem.

As described above, there are cases where the control torque greatly exceeds the torque target value during speed control, and there is a possibility that braking is not sufficiently performed when returning from the maximum operation amount. It was a challenge.

This invention is made | formed in view of the said fact, and makes it a subject to implement | achieve the turning control system which harmonized the speed control and torque control of the turning body well.

The present invention employs the following configuration as means for solving the above-described problems. That is,
The invention according to claim 1 is an operation means for generating an operation signal of the electric motor in a construction machine in which the upper revolving body is slidably mounted on the lower traveling body and the upper revolving body is driven to rotate by the electric motor. Based on speed detection means for detecting the turning speed of the upper turning body, control means for controlling the electric motor based on the operation signal of the electric motor and the turning speed of the speed detection means, and a control input signal from the control means An inverter that converts a DC power source into a driving power source for the electric motor, and a mechanical brake that holds the rotating body in a stopped state, the control means determines a target speed and a limit torque based on the operation signal, A torque value by feedback control is obtained from the deviation between the target speed and the turning speed of the speed detection means, and the torque value is compared with the limit torque to obtain the torque value having the smaller absolute value. It is characterized in together with the target speed as a click control amount that has a control input signal of the inverter.

  According to a second aspect of the present invention, in the first aspect of the present invention, the operation means is a negative operation amount, zero or positive operation with respect to the left turn, neutral or right turn of the upper swing body. The target speed and the limit torque are determined symmetrically in the negative manipulated variable interval and the positive manipulated variable interval, and the target speed is in the zero interval from the zero point of the manipulated variable to a predetermined point near zero. Is zero speed, the speed increases from zero to the maximum speed in the first section beyond the predetermined point, the maximum speed is constant in the second section exceeding the first section, and the limit torque is accelerated in the zero section during acceleration The torque increases from zero to the maximum acceleration torque in the acceleration section that exceeds zero, and is constant at the maximum acceleration torque in the final section that exceeds the acceleration section, and is constant at the maximum deceleration torque in all sections of the manipulated variable during deceleration. It is characterized in that defined such that.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the control means activates the mechanical brake when the turning is stopped to hold the stopped state of the upper turning body. In this way, the mechanical brake is released after the speed command signal is set to zero at the start of turning.

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the electric motor is a synchronous motor or an induction motor.

  As described above, according to the turning control device of the present invention, the target speed and the limit torque are defined according to the operation amount, the feedback control is performed based on the target speed, and the acceleration or braking torque is greater than the limit torque. In this case, the torque is limited so that excessive acceleration torque and deceleration torque are not applied by feedback control, and when heavy load is applied, it is automatically switched to torque control for smooth control. Can be obtained. Further, since the braking torque is always limited to the maximum, an effect of improving controllability during braking can be obtained.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an overall configuration diagram of a turning control device for a construction machine according to an embodiment of the present invention. In FIG. 1, the electric motor 11 is comprised with the three-phase synchronous motor which used the permanent magnet for the rotor, for example. The target rotational speed of the synchronous motor 11 (the rotational speed in the no-load state) is determined by the frequency of the applied three-phase AC power supply, and the actual rotational speed (the rotational speed in the loaded state) is determined by the load torque and the input power. That is, if the voltage (maximum value or effective value) of the input power is made constant, the output torque can be controlled by the input current. On the other hand, the frequency of the three-phase AC power supply is the same as the frequency of the inverter 12. The motor 11 is not limited to a three-phase synchronous motor, and may be a single-phase synchronous motor or an induction motor.

The output shaft 11 a of the electric motor 11 is connected to the speed reducer 21, and the output shaft 21 a of the speed reducer 21 is connected to the upper swing body 22. Further, a mechanical brake 23 is provided on the output shaft 11 a of the electric motor 11, and a speed detector 24 that detects the rotational speed of the electric motor 11 is provided. The speed detector 24 may be constituted by a sensor using a rotary encoder, for example. The turning speed of the upper turning body 22 is equal to the detection result of the speed detector 24 (measured value of the rotational speed of the electric motor 11) multiplied by the reduction ratio of the reduction gear 21. Therefore, the speed detector 24 of the electric motor 11 may be regarded as a turning speed detector of the upper turning body 22.

The inverter 12 is a variable frequency generator composed of a semiconductor element circuit, and based on a command signal from the control means 13, the battery power source (DC power source) 14 is changed to a three-phase AC power source having a predetermined frequency and a predetermined current. Convert. The battery power source 14 is a power source mounted on the construction machine, and is a direct current power source obtained by rectifying the alternating current generated by the generator 18 connected to the engine 16 via the speed increaser 17 by the converter 19.

  The output of the operating means 20 and the output of the speed detector 24 are connected to the input side of the control means 13, and the output side is connected to the control terminal of the inverter 12 and the control terminal of the mechanical brake 23. The operation means 20 includes an operation lever 20a and a main body 20b. The operation lever 20a is configured to be tiltable in the left, neutral, and right directions, for example, in accordance with the left turn, neutral, and right turn of the upper swing body 22. The tilt angle is converted into an electric signal by a potentiometer or the like provided in the main body 20b and output as an operation amount.

FIG. 2 shows a configuration example of the control means 13. In FIG. 2, the target determination unit 31 obtains a target speed and a limit torque corresponding to the operation amount from the operation amount conversion table 32 and the operation means 20 recorded in advance in memory, and the change direction (or differential value). decide.

The operation amount conversion table 32 is determined as shown in FIG. That is, the left turning, neutral, and right turning of the upper swing body 22, that is, the negative operation amount, zero, and the positive operation amount are assigned to the rotation direction of the motor 11, and the target speed and the limit torque of the motor 11 are The negative manipulated variable interval and the positive manipulated variable interval are defined symmetrically (point symmetrical about the origin). Furthermore, the target speed is zero in the zero section from the zero point of the manipulated variable to a predetermined point near zero, the speed increases from zero to the maximum speed in the first section beyond the zero section, and exceeds the first section In the second section, the maximum speed is constant. The limit torque is zero during acceleration, zero in the zero interval, increases from zero to the maximum acceleration torque in the acceleration interval exceeding the zero interval, becomes constant at the maximum acceleration torque in the final interval beyond the acceleration interval, and operates during deceleration. It is determined to be constant at the maximum deceleration torque in the entire section of the quantity.

  The target speed and the limit torque determined by the target determination unit 31 are input to the controller 33. The target speed and the speed of the speed detector 24 are applied to the adder 34, and the PID controller 35 obtains acceleration torque from the deviation and inputs it to the comparison unit 36. The comparison unit 36 compares the absolute values of the acceleration torque and the limit torque, and outputs the torque having the smaller absolute value to the coefficient unit 37. The coefficient unit 37 converts the torque value into a torque control signal (current) and outputs it to the inverter 12. On the other hand, the coefficient unit 38 converts the target speed into a speed control signal and outputs it to the inverter 12. The inverter 12 generates a three-phase AC power source having a predetermined frequency and a predetermined current applied to the electric motor 11 based on the torque control signal and the speed control signal.

  The activation / stop detection unit 39 detects when the operation amount shifts from the zero interval to the first (acceleration) interval and when the operation amount shifts from the first (acceleration) interval to the zero interval, and the activation control unit 40 The start signal is output to the stop control unit 41 or the stop signal is output to the stop control unit 41. The start control unit 40 outputs a mechanical brake release signal after outputting a zero speed signal for a predetermined time, and the stop control unit 41 outputs a mechanical brake holding signal.

  As described above, according to the present embodiment, there is no need to distinguish between feedback control and torque control, that is, it is not necessary to determine whether the load is light or heavy, and the control method is simplified. In addition, since excessive acceleration torque (or braking torque) exceeding the limit torque does not act during feedback control, the effect that safe control is possible, and feedback control and torque control are Since it is continuously performed, the effect of enabling smooth control is obtained. Further, since the braking torque limit is always set to the maximum during deceleration, the effect of improving the controllability during braking can be obtained.

  It should be noted that the technical scope of the present invention is not limited to the technical matters described in the above embodiment, and for example, even when a synchronous motor is used, it belongs to the technical scope of the present invention.

The structure of this embodiment is shown. The structural example of the control means of this embodiment is shown. A conversion graph of operation amount, target speed, and limit torque is shown.

Explanation of symbols

11 Three-phase synchronous motor (motor)
DESCRIPTION OF SYMBOLS 12 Inverter 13 Control means 14 Battery 20 Operation means 22 Upper turning body 23 Mechanical brake 24 Speed detector 31 Target determination part 32 Operation amount conversion table 33 Controller 39 Start / stop detection part

Claims (4)

In a construction machine in which an upper swing body is slidably mounted on a lower traveling body and the upper swing body is driven to rotate by an electric motor, an operating means for generating an operation signal of the electric motor, and a swing speed of the upper swing body are set. Speed detecting means for detecting, control means for controlling the electric motor based on an operation signal of the electric motor and a turning speed of the speed detecting means, and driving of the electric motor based on a control input signal from the control means An inverter for converting to a power source; and a mechanical brake for holding the rotating body in a stopped state, wherein the control means determines a target speed and a limit torque based on the operation signal, and the target speed and the speed detection means A torque value by feedback control is obtained from the deviation from the turning speed of the motor, the torque value is compared with the limit torque, and the torque value having the smaller absolute value is used as the torque control amount. Upper rotating body controller of the construction machine, characterized in that the control input signal of the inverter with the speed.   The operation means is assigned a negative operation amount, zero, and a positive operation amount for the left turn, neutral and right turn of the upper swing body, and the target speed and the limit torque are positive with respect to the negative operation amount section. The target speed is determined symmetrically in the manipulated variable section, and the target speed is zero in the zero section from the zero point of the manipulated variable to a predetermined point near zero, and the speed is zero to the maximum speed in the first section beyond the predetermined point. In the second section exceeding the first section, the maximum speed is constant at the maximum speed, the acceleration torque is zero in the zero section during acceleration, the acceleration torque is increased from zero to the maximum acceleration torque in the acceleration section exceeding the zero section, 2. The construction machine according to claim 1, wherein the maximum speed is constant at a maximum acceleration torque in a final section beyond the acceleration section, and is constant at a maximum deceleration torque in all sections of an operation amount during deceleration. Upper rotating body controller. The control means actuates the mechanical brake when the turning is stopped to maintain the stopped state of the upper turning body, and releases the mechanical brake after setting the speed command signal to zero when starting the turning. The turning control device for a construction machine according to any one of claims 1 and 2. The said electric motor was comprised by the synchronous motor or the induction motor, The turning control apparatus of the construction machine of any one of Claims 1-3 characterized by the above-mentioned.

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