JP2014087874A - Industrial robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem in which reliability of a robot is deteriorated by a temperature rise caused by heat radiation as the robot radiates regenerative energy of a motor as heat and energy is wasted.SOLUTION: An industrial robot includes: a storage unit for storing a program including an operation speed of a robot and information of a load attached to the robot; a motor for making the robot operate; a converter unit for converting an alternating current into a direct current; an inverter unit for converting the output of the converter unit into an alternating current and supplying it to the motor; a capacitor for smoothing the output of the converter unit; a voltage detection unit for detecting the voltage of the capacitor; a regeneration unit which is provided in parallel with the capacitor and in which a resistance part and a switching part are connected in series; a threshold value setting unit for setting a threshold value for operating the switching part; and a control unit for controlling the switching part based on the output of the voltage detection unit and output of the threshold value setting unit. The threshold value setting unit changes the threshold value during the operation of the robot based on the operation speed of the robot and the information of the load.

Description

  The present invention relates to an industrial robot having a regeneration function.

  FIG. 2 shows a main circuit of a controller for an industrial robot with conventional motor control. In FIG. 2, the part excluding the AC power supply 101 and the motor 108 is a main circuit of the control device. A rectifier circuit including a diode bridge 102 and a smoothing capacitor 103 is connected to the AC power source 101. A smoothing capacitor 103 is connected to a discharge circuit composed of a power semiconductor 104 and a resistor 105. To this discharge circuit, an inverter unit 106 composed of a plurality of switching elements 107 is connected. A motor 108 is connected to the plurality of switching elements 107 constituting the inverter unit 106. The smoothing capacitor 103 is connected to a voltage detection unit 110 that detects the power supply voltage of the motor drive circuit 109.

  When operating an industrial robot, current is applied when the motor 108 is accelerated. However, when the motor 108 is decelerated, the motor 108 is braked by absorbing the kinetic energy possessed by the operating manipulator constituting the industrial robot. For this reason, when the motor 108 decelerates, the motor 108 functions as a generator and generates electric power. The electric power generated by the motor 108 is called regenerative energy. As a method of absorbing this regenerative energy, as shown in FIG. 2, it is common to convert to heat using a resistor 105 and dissipate heat to the atmosphere.

  The regenerative energy generated by the motor 108 for driving the industrial robot flows into the motor drive circuit 109 and raises the power supply voltage (both ends voltage) of the motor drive circuit 109. If this voltage increase value becomes too large, the motor drive circuit 109 will break down the breakdown voltage. For this reason, the voltage detection unit 110 monitors the power supply voltage (voltage between both ends) of the motor drive circuit 109. When the power supply voltage becomes equal to or higher than a predetermined threshold value, the power semiconductor 104 is driven so that a current flows through the discharging resistor 105, and the regenerative energy is converted into heat by the resistor 105. As a result, regenerative energy is consumed, and the power supply voltage of the motor drive circuit 109 is maintained at a normal voltage.

  There is also known a robot control device that includes a regenerative energy absorbing means of a motor and a means for detecting the operation frequency of the regenerative energy absorbing means to prevent the regenerative energy absorbing means from being damaged due to overload (for example, Patent Document 1). reference).

JP-A-6-15590

  In the above conventional method, regenerative energy is radiated into the atmosphere as thermal energy. Therefore, energy is wasted. In addition, the temperature rise due to heat dissipation can be a factor that reduces the reliability of industrial robots.

  Moreover, in patent document 1, in order to prevent destruction by excessive operation | movement of the resistance for discharge, the operation | movement of an industrial robot is restrict | limited.

  This invention is made in view of such a subject, and operates the switching part which comprises the regeneration part during operation | movement of a manipulator based on the information of the operation speed of a manipulator, and the load attached to the manipulator. An object of the present invention is to provide an industrial robot that constantly changes the threshold value.

  In order to solve the above-described problem, an industrial robot of the present invention is an industrial robot including a manipulator and a control device that controls the operation of the manipulator, and includes an operation program including information on the operation speed of the manipulator, A storage unit for storing information on a load attached to the manipulator; a motor for operating the manipulator; a converter unit for inputting AC power to output DC power; and a plurality of switching elements. An inverter unit that inputs the output of the converter unit and supplies AC power to the motor, a capacitor that smoothes the output of the converter unit, a voltage detection unit that detects a voltage across the capacitor, and the capacitor A regenerative unit that is provided in parallel and in which a resistance unit and a switching unit are connected in series; A threshold setting unit for setting a threshold for operating the switching unit of the regeneration unit, and an operation of the switching unit of the regeneration unit based on an output of the voltage detection unit and an output of the threshold setting unit The controller includes a control unit, and the threshold setting unit changes the threshold during the operation of the manipulator based on information on an operation speed of the manipulator and a load attached to the manipulator.

  In addition to the above, the industrial robot of the present invention, in addition to the above, the threshold setting unit estimates the operating speed of the manipulator from the detection voltage of the voltage detecting unit, the threshold setting unit as the operating speed used for changing the threshold, The estimated operation speed is used.

  In addition to the above, in the industrial robot of the present invention, the threshold setting unit uses an operation speed command constituting an operation program as an operation speed used for changing the threshold.

  In addition to the above, in the industrial robot of the present invention, the threshold setting unit sets the threshold to a value higher than the withstand voltage within an allowable time during which a voltage exceeding the withstand voltage of the capacitor or the switching element can be applied. To change.

  In addition to the above, in the industrial robot of the present invention, the threshold setting unit lowers the threshold as the operation speed is slower, and increases the threshold as the operation speed is higher.

  In addition to the above, in the industrial robot of the present invention, the information on the load attached to the manipulator is the weight of the tool attached to the manipulator, and the threshold setting unit reduces the threshold as the load is lighter. The threshold value is increased as the load becomes heavier.

  As described above, according to the present invention, it is possible to provide an industrial robot that reduces the waste of releasing regenerative energy generated during the deceleration operation of the manipulator as heat energy.

The figure which shows schematic structure of the industrial robot in Embodiment 1 of this invention. The figure which shows schematic structure of the conventional industrial robot

(Embodiment 1)
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a schematic configuration of an industrial robot according to the first embodiment.

  In FIG. 1, the industrial robot includes a manipulator 1 and a control device 2 that controls the operation of the manipulator 1.

  The manipulator 1 is a 6-axis vertical articulated robot, for example, and includes a motor 3 therein. Further, a tool such as a welding torch or a painting gun (not shown) is attached to the manipulator 1 as a load. Then, based on the teaching program stored in the control device 2, the operation of the manipulator 1 is controlled by the control device 2.

  The control device 2 includes a storage unit 4, a converter unit 5, an inverter unit 6, a capacitor 7, a voltage detection unit 8, a regeneration unit 9, a threshold setting unit 10, and a control unit 11. The control device 2 also requires other components for controlling the operation of the manipulator 1, but is omitted in FIG. 1.

  The storage unit 4 stores an operation program including information on the operation speed of the manipulator 1, information on a load attached to the manipulator 1, and the like. The load information is, for example, the weight of a welding tool attached to the manipulator 1. The converter unit 5 inputs AC power from the AC power source 12 and outputs DC power. The inverter unit 6 includes a plurality of switching elements 13. The switching element 13 is connected to the motor 3 constituting the manipulator 1. The inverter unit 6 receives the DC power output from the converter unit 5, converts it into AC power, and supplies the AC power to the motor 3. The capacitor 7 smoothes the output of the converter unit 5. The voltage detector 8 detects the voltage across the capacitor 7. The regenerative unit 9 is provided in parallel to the capacitor 7 and is configured by connecting a resistor unit 14 and a switching unit 15 in series. The threshold setting unit 10 sets a threshold for operating the switching unit 15 of the regeneration unit 9. The control unit 11 controls the operation of the switching unit 15 based on the output of the voltage detection unit 8 and the output of the threshold setting unit 10.

  The operation of the industrial robot configured as described above will be described. The threshold value setting unit 10 includes an operation program including information on the operation speed of the manipulator 1, information from the storage unit 4 that stores information on a load attached to the manipulator 1, and a voltage detection unit 8 that detects a voltage across the capacitor 7. Based on the voltage information, a threshold for operating the switching unit 15 is set. The threshold setting unit 10 estimates the operating speed of the manipulator 1 based on the voltage information of the voltage detecting unit 8, and sets the threshold based on the estimated operating speed. The threshold setting unit 10 stores the relationship between the operation speed information, the load information, and the threshold value as, for example, a table or a mathematical expression. As described above, the threshold setting unit 10 determines the threshold based on the operation speed estimated from the detection voltage of the voltage detection unit 8 and the load information stored in the storage unit 4. When the detection voltage of the voltage detection unit 8 changes during operation of the manipulator 1, the threshold value is also changed. That is, the threshold value is changed during the operation of the manipulator 1.

  In the above description, the operation speed estimated from the detection voltage of the voltage detection unit 8 is used as the operation speed information for determining the threshold. However, the operation speed command constituting the teaching program may be used as information on the operation speed for determining the threshold value. And if the operation speed command which comprises a teaching program changes during operation | movement of the manipulator 1, a threshold value will also be changed.

  The control unit 11 controls the switching unit 15 based on the detection voltage detected by the voltage detection unit 8 and the threshold value determined by the threshold value setting unit 10. When the detection voltage of the voltage detection unit 8 is equal to or higher than the threshold voltage set by the threshold setting unit 10, the control unit 11 turns on the switching unit 15 to be in a conductive state so that a current flows through the resistance unit 14. To. On the other hand, when the detection voltage of the voltage detection unit 8 is lower than the threshold voltage set by the threshold setting unit 10, the control unit 11 turns off the switching unit 15 to make it non-conductive.

  As described above, the regenerative energy from the motor 3 is consumed as thermal energy by the resistance unit 14 and the capacitor 7 and the switching element 13 are protected.

  The threshold setting unit 10 lowers the threshold as the load is lighter and increases the threshold as the load is heavier. The threshold setting unit 10 lowers the threshold as the operating speed of the manipulator 1 is slow, and increases the threshold as the operating speed is fast.

  In addition, the threshold setting unit 10 sets the threshold to be higher than the breakdown voltage even if the determined threshold is higher than the breakdown voltage within an allowable time during which a voltage exceeding the breakdown voltage of the capacitor 7 or the switching element 13 can be applied. Change to a higher value. By doing in this way, the ON time of the switching part 15 can be reduced and the time for the current to flow through the resistance part 14 can be reduced. Thus, by reducing the time during which the current flows through the resistance unit 14, heat generation caused by the current flowing through the resistance unit 14 is suppressed, and the temperature rise of the industrial robot is suppressed, thereby improving the reliability of the industrial robot. Can be maintained.

  In order to appropriately suppress the temperature rise of the industrial robot, the threshold value set by the threshold value setting unit 10 is constant without changing the threshold value as is generally done conventionally. It is desirable to change within a range equal to or greater than the fixed threshold.

  Moreover, in this Embodiment 1, the structure shown in FIG. 1 is required by the number of the motors 3 which the manipulator 1 has. However, for the sake of convenience, the case where there is one motor 3 is described as an example. When the manipulator 1 includes a plurality of motors 3, the same number of inverter units 6 provided in the control device 2 as the motors 3 used in the manipulator 1 are provided in parallel.

  INDUSTRIAL APPLICATION This invention can reduce the waste which discharge | releases the regenerative energy which generate | occur | produces at the time of the deceleration operation of a manipulator as heat energy, and is industrially useful as an industrial robot which controls a motor with an inverter.

DESCRIPTION OF SYMBOLS 1 Manipulator 2 Control apparatus 3 Motor 4 Memory | storage part 5 Converter part 6 Inverter part 7 Capacitor 8 Voltage detection part 9 Regenerative part 10 Threshold setting part 11 Control part 12 AC power supply 13 Switching element 14 Resistance part 15 Switching part

Claims (6)

An industrial robot comprising a manipulator and a control device for controlling the operation of the manipulator,
A storage unit for storing an operation program including information on the operation speed of the manipulator and information on a load attached to the manipulator;
A motor for operating the manipulator;
A converter unit for inputting AC power and outputting DC power;
An inverter unit which has a plurality of switching elements and inputs the output of the converter unit to supply AC power to the motor;
A capacitor for smoothing the output of the converter unit;
A voltage detector for detecting a voltage across the capacitor;
A regenerative unit that is provided in parallel with the capacitor and in which a resistance unit and a switching unit are connected in series;
A threshold setting unit for setting a threshold for operating the switching unit of the regeneration unit;
A control unit that controls the operation of the switching unit of the regeneration unit based on the output of the voltage detection unit and the output of the threshold value setting unit;
The threshold setting unit is an industrial robot that changes the threshold during the operation of the manipulator based on information on an operation speed of the manipulator and a load attached to the manipulator. The industrial robot according to claim 1, wherein the threshold setting unit estimates an operation speed of the manipulator from a detection voltage of the voltage detection unit, and the threshold setting unit uses the estimated operation speed as an operation speed used for changing the threshold. . The industrial robot according to claim 1, wherein the threshold setting unit uses an operation speed command constituting an operation program as the operation speed used for changing the threshold. 4. The threshold value setting unit according to claim 1, wherein the threshold value setting unit changes the threshold value to a value higher than the withstand voltage within an allowable time during which a voltage exceeding the withstand voltage of the capacitor or the switching element can be applied. Industrial robot. The industrial robot according to any one of claims 1 to 4, wherein the threshold value setting unit lowers the threshold value as the operation speed is slower and increases the threshold value as the operation speed is faster. The information on the load attached to the manipulator is the weight of the tool attached to the manipulator, and the threshold setting unit lowers the threshold as the load is lighter, and increases the threshold as the load is heavy. The industrial robot according to any one of claims 1 to 5.

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