Patent Description:
Conventionally, in a machine tool or the like, in order to dispose a regenerative energy generated when a servo motor driving a rotational axis of a movable portion thereof is slowed down, a system comprising both a resistance regenerating function of consuming regenerative energy in a regenerative resistor and a power supply regenerating function of regenerating the regenerative energy on an AC power supply side is known (PLT <NUM>).

In contrast, in a industry robot, the regenerative energy generated when a servo motor connected to a rotational axis of a movable portion of a robot arm or the like is slowed down is usually smaller than the regenerative energy generated when a servo motor driving a rotational axis of a movable portion of a machine tool or the like is slowed down. Therefore, when the regenerative energy is expected to increase according to an increase of operation load factor of a robot, reinforcing the resistance regenerating function has been general rather than adding the power supply regenerating function.

However, also in an industrial robot, the regenerative energy generated in a servo motor becomes extremely large when an operation is performed at an extremely high load factor (repeating start/stop frequently), and therefore it is desirable to comprise the power supply regenerating function of regenerating the electric power into the power supply in addition to the resistance regenerating function of consuming the regenerative energy by the regenerative resistor. <CIT> relates to an electric motor control device for an elevator which performs variable voltage variable frequency control of a plurality of car driving motors for an elevator. <CIT> relates to a servomotor drive device having a first converter, a regenerative resistor circuit having a first switching element and a regenerative resistor, a first connection part configured to connect a second converter in parallel to the regenerative resistor circuit in an attachable and detachable manner, and a first control unit configured to control the on and off states of the first switching element. <CIT> relates to an electric power regeneration method which involves forming of operation plan of combined redundant robot to take energy demand and supply balance, and operating of redundant robot with other combined mechanical apparatus based on operation plan.

Note that, when necessary functions are added and deleted according to work contents required by a user in an industrial robot, basic components driving the robot body need to be changed for each user, increasing the development cost.

Also the case that the power supply regenerating function is added to the industrial robot is no exception, and it is necessary to design a control portion exclusive for power supply regeneration and incorporate the same into a robot control system in order to add the power supply regenerating function to the robot control system, causing a problem that the development cost is increased.

The present invention is made considering the above-mentioned problems of the conventional art and its object is to provide a robot control system capable of suppressing the increase of the development cost and adding the power supply regenerating function.

In order to achieve the above-mentioned objects, the industrial robot according to the present invention is defined by the subject matter of independent claim <NUM>, with preferred embodiments defined in the dependent claims.

According to the present invention, a robot control system capable of suppressing increase of the development cost and adding the power supply regenerating function can be provided.

Hereunder, a robot control system according to an embodiment of the present invention will be described referring to <FIG>.

In a robot control system <NUM> illustrated in <FIG>, an AC current from a three-phase AC power supply <NUM> is supplied to a converter <NUM> having a plurality of (six in the example) diodes (rectifier elements) <NUM>, and the AC current is converted into a DC current in the converter <NUM>. The DC current generated in the converter <NUM> is supplied to a plurality of (N in the example) inverters (DC-AC switching devices) <NUM> (5A, 5N).

The number N of installed inverters <NUM> is determined according to the number of drive shafts and external axes of a robot. For example, when a six-axis articulated robot has three external axes, the number N of installed inverters <NUM> is nine (six and three makes nine).

Each inverter <NUM> has a plurality of (six in the example) diodes <NUM> and a plurality of (six in the example) switching elements <NUM> each connected in parallel with the corresponding one of the plurality of diodes <NUM>. Each inverter <NUM> inverts the DC current supplied from the converter <NUM> into an AC current and supplies the same into each servo motor <NUM> (8A, 8N). Motor sensors (encoders) <NUM> (9A, 9N) are attached to their respective servo motors <NUM>.

A resistance regenerating circuit <NUM> is provided between the converter <NUM> and the inverters <NUM>. The resistance regenerating circuit <NUM> is configured by connecting a regenerative resistor <NUM> and a switching element <NUM> in series.

The robot control system <NUM> according to the embodiment further comprises a servo control device (servo board) <NUM> for controlling drive of the servo motors <NUM>. The servo control device <NUM> has a plurality of (N in the example) motor control portions <NUM> (14A, 14N) for controlling the respective servo motors <NUM> and a plurality of (N in the example) control port portions <NUM> (15A, 15N) corresponding to the plurality of motor control portions <NUM>. Each motor control portion <NUM> controls drive of the corresponding servo motor <NUM> based on a signal from the corresponding motor sensor <NUM> attached to the same servo motor <NUM>.

Additionally, each of the plurality of motor control portions <NUM> includes a power supply regenerating control function portion <NUM> (16A, 16N) for controlling a power supply regenerating circuit and also is configured so that the power supply regenerating control function portion <NUM> and a control function portion <NUM> (17A, 17N) for the servo motor <NUM> can be switched. The power supply regenerating control function portion <NUM> and the control function portion <NUM> for the servo motor <NUM> may be switched by changing settings or automatic detection.

Hereunder, in the robot control system <NUM> according to the embodiment, an example that the motor control portion 14N for a N axis (external axis) is used for power supply regeneration will be described.

First, when the motor control portion 14N for the N axis is used not for power supply regeneration but for controlling drive of the servo motor 8N of the N axis, a connector 18N of the servo motor 9N of the N axis is connected to a connector 19N of the inverter 5N for the N axis and also the inverter 5N for the N axis is connected to a port 20N for PWM of the control port portion 15N for the N axis. Also, a connector 21N of the motor sensor 9N attached to the servo motor 8N of the N axis is connected to a port 22N for sensor communication of the control port portion 14N for the N axis via a wiring 23N for sensor communication.

In contrast, when the motor control portion 14N for the N axis is used not for controlling drive of the servo motor 8N of the N axis but for power supply regeneration, a reactor <NUM> is connected to the three-phase AC power supply <NUM> and also a primary voltage sensor portion (phase detection portion) <NUM> for detecting primary voltage is provided to a wiring <NUM> connecting the reactor <NUM> and the three-phase AC power supply <NUM>.

Additionally, a connector <NUM> of the primary voltage sensor portion <NUM> is connected to the port 22N for sensor communication of the control port portion 14N for the N axis. Further, the connector <NUM> of the reactor <NUM> is connected to the connector 19N of the inverter 5N for the N axis. Here, the inverter 5N for the servo motor 8N of the N axis comprises a configuration in common with an inverter configuring a power supply regenerating circuit, and the both can be used in common.

Note that a communication format (protocol) for motor control (encoder) and a communication format (protocol) for power supply regeneration (primary voltage sensor portion) are made common.

As above, when the motor control portion 14N for the N axis is used for power supply regeneration, change of settings or automatic detection enables switching from the control function portion 17N for the servo motor 8N of the N axis to the power supply regenerating function portion 16N.

In the robot control system <NUM> according to the embodiment above, when the level of a P-N smoothing capacitor <NUM> provided between the resistance regenerating circuit <NUM> and the inverter <NUM> is below a predetermined value, the power supply regenerating function by the power supply regenerative circuit including the inverter 5N for the N axis, reactor <NUM>, and the primary voltage sensor portion <NUM> works. In contrast, when the level of the smoothing capacitor <NUM> of PN becomes the predetermined value or more, the regenerative energy is consumed in the resistance regenerating circuit <NUM>.

As above, in the robot control system <NUM> according to the embodiment, the power supply regenerating control function portion <NUM> is standardly implemented in the servo control device <NUM> controlling drive of the servo motor <NUM>, and one of the plurality of control ports <NUM> which have been previously prepared in the servo control device <NUM> is diverted so as to switch and properly select whether the port is used as a motor control port or a power supply regenerating port by changing settings or automatic detection. Therefore, a new control portion for power supply regenerating control does not need to be provided even when the power supply regenerating function is added corresponding to requests of a user. Thereby, increase of the development cost according to addition of the power supply regenerating function can be suppressed.

Also, as the power supply regenerating function can be provided by diverting the inverter <NUM> for robot control, it is not necessary to develop a new inverter for power supply regeneration separately, and therefore increase of the development cost according to addition of the power supply regenerating function can be further suppressed.

Note that, although the case that the motor control portion 14N for the N axis is used for power supply regeneration is described in the example above, the motor control portion <NUM> used for power supply regeneration is not limited to that for the N axis. For example, using the motor control portion 14A for a first axis for power supply regeneration is also possible, and the port 20A for PWM of the control port 15A for the first axis and the port 22A for sensor communication are used for power supply regeneration in the case.

<FIG> illustrates a configuration when the regenerating function is reinforced in a conventional robot control system.

As illustrated in <FIG>, in a conventional robot control system <NUM>, a motor control portion <NUM> of a servo control device thereof does not comprise the power supply regenerating control function. Therefore, a regenerative resistor <NUM> is added to the resistance regenerating circuit <NUM> in order to deal with increase of the regenerative energy. Namely, the additional regenerative resistor <NUM> is provided in parallel with the standardly mounted regenerative resistor <NUM>.

In the conventional method above, there is a problem from the viewpoint of effective utilization of energy as well, since coping with considerable increase of the regenerative energy is difficult and also regenerative energy consumption is increased.

Claim 1:
An industrial robot comprising a control system (<NUM>), the control system comprising:
a converter (<NUM>) configured to convert an AC current from an AC power supply (<NUM>) into a DC current;
an inverter (<NUM>) configured to invert a DC power supplied from the converter (<NUM>) into an AC power;
a servo control device configured to control a drive of a plurality of servo motors (<NUM>) based on a signal from a motor sensor (<NUM>) attached to the servo motors (<NUM>), and
a resistance regenerating circuit (<NUM>) configured to consume a regenerative energy generated in the servo motors (<NUM>),
wherein the servo control device (<NUM>) has a plurality of motor control portions (<NUM>) configured to enable the plurality of servo motors (<NUM>) to be controlled and a plurality of control port portions (<NUM>) corresponding to the plurality of motor control portions (<NUM>),
wherein at least one of the plurality of motor control portions (<NUM>) has a power supply regenerating control function portion (<NUM>) configured to control a power supply regenerating circuit including an inverter having a configuration in common with the inverter (<NUM>) for the servo motor so as to be used in common for both functions of regeneration and motoring and is configured such that the power supply regenerating control function portion (<NUM>) and a control function portion (<NUM>) for the servo motor (<NUM>) can be switched depending on whether an object to be connected to the control port portion (<NUM>) is the power supply regenerating circuit or the servo motor (<NUM>),
characterized in that, the power supply regenerating circuit further comprises a reactor (<NUM>) connected to the AC power supply (<NUM>) and a primary voltage sensor portion (<NUM>) connected to a wiring (<NUM>) connecting the reactor and the AC current power supply so as to detect a primary voltage, the reactor (<NUM>) being connected to the inverter (<NUM>) to be used in common for both functions of regeneration and motoring, and the primary voltage sensor portion (<NUM>) being connected to the at least one of the plurality of motor control portions (<NUM>).