Patent Description:
Conventionally, a robot controller as disclosed in Patent Literature <NUM> has been known. Patent Literature <NUM> discloses, regarding the robot controller, that when a main power supply is not connected to a third connection and a power supply for maintenance is connected to a fourth connection, voltage from the power supply for maintenance is supplied to a brake drive circuit. As a result, the brake of a robotic arm is unlocked.

In Patent Literature <NUM>, the power supply for maintenance supplies electric power to the brake (non-excitation actuated electromagnetic brake) when the brake is not supplied with electric power from the main power supply, thereby switching the brake from a brake-applied state to a brake-released state. Thus, even when the brake is not supplied with electric power from the main power supply, the posture of the robot can be changed, which makes it possible to perform maintenance work or the like on the robot.

However, Patent Literature <NUM> has a problem in that when the brake is released, the posture of the robot suddenly changes (e.g., the robotic arm suddenly falls due to its own weight), which causes a danger. In order to solve such a problem, conventionally, for example, as shown in <FIG>, a robotic arm <NUM> is in advance suspended by, for example, a crane <NUM>, and thereby such a sudden fall of the robotic arm is prevented. However, such a conventional preventative measure is labor and time consuming.

Patent Literature <NUM>, which forms the basis for the preamble of claim <NUM>, discloses a device for releasing the motor brake of an articulated robot. The device is provided with braking resistance connected between each terminal of a motor provided in each joint of the articulated robot, and electromagnetic brake releasing switches provided for every motor of each joint to release the electromagnetic brake of the motor. When releasing the electromagnetic brake by the electromagnetic brake releasing switches, the lowering operation by self weight of the robot arm connected to the motor is braked by dynamic electric braking of the motor corresponding to the released electromagnetic brake.

Further exemplary robot systems are known from Patent Literatures <NUM> and <NUM>.

In view of the above, an object of the present invention is to provide: a robot system including a short-circuiting device that makes it possible to readily stabilize the posture of a robot.

In order to solve the above-described problems, a robot system according to claim <NUM> includes a robot including a robotic arm, at least one motor, and at least one non-excitation actuated electromagnetic brake that is provided for the respective at least one motor, the robotic arm including at least one joint shaft that is provided with the respective at least one motor; a short circuit that is electrically connected to the robot and provided separately from a robot controller configured to control the robot, the short circuit being configured to apply a dynamic brake to each motor.

According to the above configuration, a change in the posture of the robot can be suppressed by short-circuiting electrodes of the motor by the short circuit. Consequently, the short-circuiting device according to the present invention makes it possible to readily stabilize the posture of the robot.

The robot system further includes at least one non-excitation actuated electromagnetic brake provided for the respective at least one motor. The short-circuiting device further includes an auxiliary power supply configured to supply electric power to the non-excitation actuated electromagnetic brake when the non-excitation actuated electromagnetic brake is not supplied with electric power from a main power supply of the robot.

According to the above configuration, the dynamic brake can be applied to each motor by the short circuit while releasing each non-excitation actuated electromagnetic brake by the auxiliary power supply. Consequently, a sudden change in the posture of the robot can be prevented, and the robot can be brought into a state in which the posture of the robot can be changed as desired.

The robot system may further include an auxiliary power supply switch configured to switch whether or not to supply electric power to the non-excitation actuated electromagnetic brake by the auxiliary power supply.

The above configuration makes it possible to release the non-excitation actuated electromagnetic brake at a desired timing.

The motor may be a three-phase motor including three electrodes. The short circuit may be configured to short-circuit two of, or all of, the three electrodes of the three-phase motor.

According to the above configuration, for example, as compared to a case where the motor is a single-phase motor, rotating magnetic fields can be obtained without special devising, and also, greater output power can be obtained.

The short-circuiting device may be configured to short-circuit electrodes of the motor by the short circuit at a same time as the short-circuiting device is mounted to the robot.

This configuration makes it possible to assuredly apply the dynamic brake before the non-excitation actuated electromagnetic brake is released.

The short-circuiting device may further include a short-circuit switch configured to switch whether or not to short-circuit electrodes of the motor by the short circuit.

The above configuration makes it possible to release the dynamic brake at a desired timing.

In order to solve the above-described problems, a robot system according to the present invention includes: a robot including a robotic arm and at least one motor, the robotic arm including at least one joint shaft that is provided with the respective at least one motor; and any one of the above-described short-circuiting devices.

According to the above configuration, a change in the posture of the robot can be suppressed by short-circuiting electrodes of the motor by the short circuit. Consequently, the robot system according to the present invention makes it possible to readily stabilize the posture of the robot.

The present invention is able to provide: a short-circuiting device that makes it possible to readily stabilize the posture of a robot; and a robot system including the short-circuiting device.

Hereinafter, a short-circuiting device and a robot system including the same according to an embodiment of the present invention are described with reference to the drawings. In the drawings, the same or corresponding elements are denoted by the same reference signs, and repeating the same descriptions is avoided below.

<FIG> is a schematic diagram showing an overall configuration of the robot system according to the embodiment of the present invention when a robot controller is mounted to a robot in the robot system. <FIG> is a simplified circuit diagram showing electrical connections when the robot controller is mounted to the robot.

A shown in <FIG>, a robot system <NUM> according to the present embodiment includes: a robot <NUM> including a robotic arm <NUM>; a robot controller <NUM> with a main power supply <NUM> incorporated therein, the robot controller <NUM> being configured to control the robot <NUM>; and a short-circuiting device <NUM> (see <FIG>) according to the present invention. The short-circuiting device <NUM> will be described below.

The robot <NUM> includes: the robotic arm <NUM>; motors <NUM> provided for six joint shafts JT1 to JT6 of the robotic arm <NUM>, respectively; and non-excitation actuated electromagnetic brakes <NUM> provided for the motors <NUM>, respectively. The robot <NUM> according to the present embodiment further includes: a base <NUM> coupled to the proximal end portion of the robotic arm <NUM>; an unshown end effector mounted to the distal end portion of the robotic arm <NUM>; and a mounting receiving portion <NUM>, to which the robot controller <NUM> or the short-circuiting device <NUM> is mounted.

As shown in <FIG>, the robotic arm <NUM> is a multi-jointed arm that includes the six joint shafts JT1 to JT6 and six links 40a to 40f. The six links 40a to 40f are sequentially coupled by these joint shafts.

A coupled body of links and joint shafts is formed by the first joint shaft JT1, the first link 40a, the second joint shaft JT2, the second link 40b, the third joint shaft JT3, and the third link 40c. The coupled body of links and joint shafts constitutes a first arm part <NUM>. Specifically, the first joint shaft JT1 couples the base <NUM> and the proximal end portion of the first link 40a in a manner to be rotatable about a vertical axis. The second joint shaft JT2 couples the distal end portion of the first link 40a and the proximal end portion of the second link 40b in a manner to be rotatable about a horizontal axis. The third joint shaft JT3 couples the distal end portion of the second link 40b and the proximal end portion of the third link 40c in a manner to be rotatable about a horizontal axis.

Another coupled body of links and joint shafts is formed by the fourth joint shaft JT4, the fourth link 40d, the fifth joint shaft JT5, the fifth link 40e, the sixth joint shaft JT6, and the sixth link 40f. This other coupled body of links and joint shafts constitutes a second arm part <NUM>. Specifically, the fourth joint shaft JT4 couples the distal end portion of the third link 40c and the proximal end portion of the fourth link 40d in a manner to be rotatable about an axis extending in the longitudinal direction of the third link 40c. The fifth joint shaft JT5 couples the distal end portion of the fourth link 40d and the proximal end portion of the fifth link 40e in a manner to be rotatable about an axis extending in a direction orthogonal to the longitudinal direction of the fourth link 40d. The sixth joint shaft JT6 couples the distal end portion of the fifth link 40e and the proximal end portion of the sixth link 40f in a manner to be rotatable in a twisting fashion. The aforementioned unshown end effector is mounted to the distal end portion of the sixth link 40f.

The motors <NUM> are provided for the six joint shafts JT1 to JT6 of the robotic arm <NUM>, respectively. <FIG> shows only one motor <NUM>. Since the other five motors <NUM> are configured in the same manner as the one motor <NUM>, the illustration and description of the other five motors <NUM> are omitted herein. As shown in <FIG>, each motor <NUM> according to the present embodiment is a three-phase motor. The three phases are a U phase, a V phase, and a W phase.

For example, each motor <NUM> is a servomotor that is servo-controlled by the robot controller <NUM>. The motors <NUM> are provided with position detectors <NUM>, respectively. Each of the position detectors <NUM> detects the rotational position of a corresponding one of the motors <NUM>. Each position detector <NUM> is, for example, an encoder.

<FIG> shows one example of a configuration including the motor, the non-excitation actuated electromagnetic brake, and the position detector. It should be noted that, in the description below, the term "load side" refers to a load-mounting side of the motor <NUM>. Specifically, in this example, the load side is the side on which a shaft <NUM> protrudes (i.e., the lower side of <FIG>), and also, the term "non-load side" refers to the opposite side to the load side (i.e., the upper side of <FIG>).

As shown in <FIG>, the motor <NUM> includes: the shaft <NUM>; a frame <NUM>; a load-side bracket <NUM> provided on the load-side end portion of the frame <NUM>; and a non-load-side bracket (which is hereinafter also called "plate") <NUM> provided on the non-load-side end portion of the frame <NUM>. The load-side bracket <NUM> and the non-load-side bracket (plate) <NUM> are provided with an unshown load-side bearing and an unshown non-load-side bearing, respectively. The shaft <NUM> is rotatably supported via these bearings.

The motor <NUM> includes: a rotor <NUM> provided on the shaft <NUM>; and a stator <NUM> provided on the inner circumferential surface of the frame <NUM>. For example, the rotor <NUM> is provided with a plurality of unshown permanent magnets. The stator <NUM> includes: an unshown stator core disposed in an annular manner; and a plurality of unshown armature windings wound around a plurality of teeth of the stator core.

The motors <NUM> are provided with the non-excitation actuated electromagnetic brakes <NUM>, respectively. Each non-excitation actuated electromagnetic brake <NUM> is configured to be applied to keep the robot <NUM> in the same posture when not being supplied with electric power, and to be released when being supplied with electric power.

As shown in <FIG>, the non-excitation actuated electromagnetic brake <NUM> is disposed at the non-load side of the motor <NUM>, and is configured to keep the shaft <NUM> stopped or to brake the shaft <NUM>. It should be noted that the non-excitation actuated electromagnetic brake <NUM> may be disposed at the load side of the motor <NUM>. The non-excitation actuated electromagnetic brake <NUM> is covered by an unshown brake cover. The non-excitation actuated electromagnetic brake <NUM> includes: a cylindrical field core <NUM>; an annular armature <NUM> disposed in a manner to face the load side of the field core <NUM>; and a brake disc <NUM> disposed between the armature <NUM> and the plate (non-load-side bracket) <NUM>.

The field core <NUM> is fixed to the plate (non-load-side bracket) <NUM> by a bolt <NUM>. The field core <NUM> is provided with a plurality of brake springs <NUM>. The brake springs <NUM> press the armature <NUM> to urge the armature <NUM> to the load side. The field core <NUM> is also provided with a coil <NUM>. The coil <NUM>, when an electric current is supplied thereto, generates magnetic suction force to suck the armature <NUM> to the non-load side against the urging force of the brake springs <NUM>. The armature <NUM> is made of a magnetic material (e.g., a steel plate).

The brake disc <NUM> is fixed to the shaft <NUM> via a hub <NUM>. Annular brake linings <NUM> are attached to both the load-side surface and the non-load-side surface of the brake disc <NUM>, respectively. The brake disc <NUM> is configured to be slidable in the axial direction of the shaft <NUM>.

The non-excitation actuated electromagnetic brake <NUM> is configured such that, while no electric current is being supplied to the coil <NUM> (i.e., non-excitation state), the armature <NUM> is pressed toward the plate <NUM> (i.e., to the load side) by the urging force of the brake springs <NUM>. As a result, the brake disc <NUM> and the brake linings <NUM> are sandwiched between the armature <NUM> and the plate <NUM>. At the time, a gap G is formed between the field core <NUM> and the armature <NUM>. Consequently, while the power supply is being cut off, the shaft <NUM> is kept stopped or the rotation of the shaft <NUM> is braked, which is a state where the non-excitation actuated electromagnetic brake <NUM> is being applied.

On the other hand, while an electric current is being applied to the coil <NUM> (i.e., excitation state), the armature <NUM> is moved toward the coil <NUM> (i.e., to the non-load side) by the magnetic suction force generated by the coil <NUM>. As a result, the same amount of gap as the gap G is formed between the armature <NUM> and the plate <NUM>, and thereby the brake disc <NUM> and the brake linings <NUM> become free. Consequently, while the motor <NUM> is in operation, the brake disc <NUM> is released from the braking, and the shaft <NUM> is rendered rotatable, which is a state where the non-excitation actuated electromagnetic brake <NUM> is released.

The position detector <NUM> is disposed at the non-load side of the non-excitation actuated electromagnetic brake <NUM>, and is coupled to the shaft <NUM>. It should be noted that the position detector <NUM> may be disposed at a different position, for example, between the motor <NUM> and the non-excitation actuated electromagnetic brake <NUM>. The position detector <NUM> detects the rotational position of the motor <NUM> by detecting the rotational position (e.g., rotational angle) of the shaft <NUM>, and outputs the detected position data. It should be noted that, in addition to or instead of the rotational position of the motor <NUM>, the position detector <NUM> may detect at least one of the speed (e.g., rotational speed or angular speed) of the motor <NUM> and the acceleration (e.g., rotational acceleration or angular acceleration) of the motor <NUM>.

As shown in <FIG>, the robot controller <NUM> is electrically connected to the robot <NUM> as a result of a mounting portion <NUM> of the robot controller <NUM> being mounted to the mounting receiving portion <NUM> of the robot <NUM>. The robot controller <NUM> incorporates therein the following components: the main power supply <NUM> of the robot <NUM>; a main power supply switch <NUM> configured to switch whether or not to supply electric power to the robot <NUM> by the main power supply <NUM>; a servo amplifier <NUM> electrically connected to the U phase, the V phase, and the W phase of the motor <NUM>; and a switch <NUM> provided between the motor <NUM> and the servo amplifier <NUM> and configured to switch whether or not to short-circuit the U phase and the V phase of the motor <NUM>.

A specific configuration of the robot controller <NUM> for controlling the operation of the robot <NUM> is not particularly limited. As one example, the control of the operation of the robot <NUM> may be realized as a result of a known processor (such as a CPU) operating in accordance with a program stored in a storage unit (e.g., a memory).

The robot controller <NUM> may include an unshown power converter that controls the rotation of each motor <NUM> while controlling the supply of electric power to each motor <NUM>. The power converter is a device configured to convert DC power supplied from the main power supply <NUM> into AC power, and may be, for example, a three-phase bridge inverter circuit including six semiconductor switching elements. For example, the six semiconductor switching elements may be constituted by six IGBTs with antiparallel-connected freewheeling diodes.

<FIG> is a schematic diagram showing an overall configuration of the robot system according to the embodiment of the present invention when the short-circuiting device is mounted to the robot in the robot system. <FIG> is a simplified circuit diagram showing electrical connections when the short-circuiting device is mounted to the robot. As shown in <FIG>, the short-circuiting device <NUM> according to the present embodiment is mounted to the robot <NUM> in a case where the robot controller <NUM> is not mounted to the robot <NUM>. Specifically, similar to the aforementioned mounting portion <NUM> of the robot controller <NUM>, the short-circuiting device <NUM> is electrically connected to the robot <NUM> as a result of a mounting portion <NUM> of the short-circuiting device <NUM> being mounted to the mounting receiving portion <NUM> of the robot <NUM>.

As shown in <FIG>, the short-circuiting device <NUM> includes: an auxiliary power supply <NUM> configured to supply electric power to each non-excitation actuated electromagnetic brake <NUM> when the non-excitation actuated electromagnetic brake <NUM> is not supplied with electric power from the main power supply <NUM>; and a short circuit <NUM> configured to apply a dynamic brake to each motor <NUM>. The short-circuiting device <NUM> according to the present embodiment further includes an auxiliary power supply switch <NUM> configured to switch whether or not to supply electric power to each motor <NUM> by the auxiliary power supply <NUM>.

When the non-excitation actuated electromagnetic brake <NUM> is not supplied with electric power from the main power supply <NUM>, the auxiliary power supply <NUM> supplies electric power to the non-excitation actuated electromagnetic brake <NUM> to bring the non-excitation actuated electromagnetic brake <NUM> into a released state. It should be noted that the auxiliary power supply <NUM> is intended for supplying electric power to the non-excitation actuated electromagnetic brake <NUM>. Therefore, unlike the above-described robot controller <NUM>, the auxiliary power supply <NUM> does not include a power supply device intended for the motor (e.g., main power supply <NUM>).

The short circuit <NUM> is configured to short-circuit all of the three electrodes (U-phase electrode, V-phase electrode, and W-phase electrode) of the motor <NUM> to each other. It should be noted that the short circuit <NUM> may be configured to short-circuit two electrodes (i.e., U-phase and V-phase electrodes, U-phase and W-phase electrodes, or V-phase and W-phase electrodes,) among the three electrodes of the motor <NUM>. As shown in <FIG>, when the short-circuiting device <NUM> is electrically connected to the robot <NUM> (i.e., when the mounting portion <NUM> is mounted to the mounting receiving portion <NUM>), the short circuit <NUM> is configured to short-circuit all of the three electrodes of the motor <NUM> to each other. That is, the short-circuiting device <NUM> according to the present embodiment is configured to short-circuit the electrodes of the motor <NUM> by the short circuit <NUM> at the same time as the short-circuiting device <NUM> is mounted to the robot <NUM>.

According to the short-circuiting device <NUM> of the present embodiment, a change in the posture of the robot <NUM> can be suppressed by short-circuiting the electrodes of the motor <NUM> to each other by the short circuit <NUM>. Consequently, the short-circuiting device <NUM> according to the present invention makes it possible to readily stabilize the posture of the robot <NUM>.

The short-circuiting device <NUM> according to the present embodiment includes the auxiliary power supply <NUM> configured to supply electric power to each non-excitation actuated electromagnetic brake <NUM> when the non-excitation actuated electromagnetic brake <NUM> is not supplied with electric power from the main power supply <NUM>. Accordingly, the dynamic brake can be applied to each motor <NUM> by the short circuit <NUM> while releasing each non-excitation actuated electromagnetic brake <NUM> by the auxiliary power supply <NUM>. Consequently, a sudden change in the posture of the robot <NUM> can be prevented, and the robot <NUM> can be brought into a state in which the posture of the robot <NUM> can be changed as desired. This makes it possible to suitably perform, for example, maintenance work or the like on the robot <NUM>.

Moreover, the short-circuiting device <NUM> according to the present embodiment further includes the auxiliary power supply switch <NUM> configured to switch whether or not to supply electric power to the non-excitation actuated electromagnetic brake <NUM> by the auxiliary power supply <NUM>. This makes it possible to release the non-excitation actuated electromagnetic brake <NUM> at a desired timing. Accordingly, after the short-circuiting device <NUM> is mounted to the robot <NUM>, for example, safety is secured, and then electric power is supplied from the auxiliary power supply <NUM> to the non-excitation actuated electromagnetic brake <NUM>. In this manner, a danger that might occur when electric power is supplied from the auxiliary power supply <NUM> can be prevented.

Furthermore, in the present embodiment, the motor <NUM> is a three-phase motor, and the short circuit <NUM> is configured to short-circuit the three electrodes of the three-phase motor to each other. Accordingly, for example, as compared to a case where the motor <NUM> is a single-phase motor, rotating magnetic fields can be obtained without special devising, and also, greater output power can be obtained.

Further, the short-circuiting device <NUM> according to the present embodiment is configured to short-circuit the electrodes of the motor <NUM> by the short circuit <NUM> at the same time as the short-circuiting device <NUM> is mounted to the robot <NUM>. This makes it possible to assuredly apply the dynamic brake before the non-excitation actuated electromagnetic brake <NUM> is released. Therefore, for example, an erroneous operation that might occur in the case of being equipped with a short-circuit switch for switching whether or not to short-circuit the electrodes of the motor <NUM> by the short circuit <NUM> (e.g., an erroneous operation that causes a situation where both the non-excitation actuated electromagnetic brake <NUM> and the dynamic brake are not being applied) can be prevented.

It should be noted that the robot system <NUM> according to the present embodiment includes: the robot <NUM> including the robotic arm <NUM> and the motors <NUM>, the robotic arm <NUM> including the six joint shafts JT1 to JT6, which are provided with the respective motors <NUM>; and the above-described short-circuiting device <NUM>. According to this configuration, the posture of the robot <NUM> can be readily stabilized.

The foregoing description has described the case in which the short-circuiting device <NUM> according to the above embodiment includes the auxiliary power supply <NUM> configured to supply electric power to the non-excitation actuated electromagnetic brake <NUM>.

For example, in the case of packing up the robot while keeping the robot in a desired posture by using a fixing jig, the short-circuiting device <NUM> according to the present variation shown in <FIG> may be mounted to the robot, and thereby the dynamic brake may be applied to the motor <NUM> so that the posture of the robot will hardly change. Consequently, for example, at the time of unpacking and installing the robot, a sudden change in the posture of the robot can be prevented when removing the fixing jig from the robot.

Generally speaking, the motor <NUM> of a conventional horizontal articulated robot is not provided with a non-excitation actuated electromagnetic brake. Therefore, the short-circuiting device <NUM> according to the above variation is particularly advantageously applicable to, for example, such a horizontal articulated robot. It should be noted that, in such a horizontal articulated robot, generally speaking, a dynamic brake is applied to the motor <NUM> as necessary by a short circuit included in a robot controller.

The above embodiment has described the case in which the robot controller <NUM> is mounted to the robot <NUM> in a detachable manner. However, the present invention is not thus limited. The robot controller <NUM> may be mounted to the robot <NUM> in a non-detachable manner. For example, the robot controller <NUM> may be incorporated in the robot <NUM>. In such a case, for example, after the robot controller <NUM> is turned OFF, the short-circuiting device <NUM> according to the present invention may be mounted to the robot <NUM>.

The above embodiment has described the case in which the motor <NUM> is configured as a three-phase motor. However, the present invention is not thus limited. For example, the motor <NUM> may be configured as a single-phase motor.

The foregoing description has described the case in which the short-circuiting device <NUM> according to the above embodiment is configured to short-circuit all of the three electrodes of the motor <NUM> by the short circuit <NUM> at the same time as the short-circuiting device <NUM> is mounted to the robot <NUM>. However, the present invention is not thus limited. Specifically, the short-circuiting device <NUM> may further include a short-circuit switch configured to switch whether or not to short-circuit the electrodes of the motor <NUM> by the short circuit. This makes it possible to release the dynamic brake at a desired timing. Consequently, for example, when the non-excitation actuated electromagnetic brake <NUM> is in a released state as a result of being supplied with electric power from the auxiliary power supply <NUM>, the dynamic brake may also be resealed after the safety is secured, and thereby the posture of the robot <NUM> may be rendered readily changeable. This makes it possible to more readily perform maintenance work or the like on the robot <NUM>.

Claim 1:
A robot system (<NUM>) comprising:
a robot (<NUM>) including a robotic arm (<NUM>), at least one motor (<NUM>), and at least one non-excitation actuated electromagnetic brake (<NUM>) that is provided for the respective at least one motor (<NUM>), the robotic arm (<NUM>) including at least one joint shaft (JT1 to JT6) that is provided with the respective at least one motor (<NUM>); and
a short circuit (<NUM>) that is electrically connected to the robot (<NUM>) and provided separately from a robot controller (<NUM>) configured to control the robot (<NUM>), the short circuit (<NUM>) being configured to apply a dynamic brake to each motor (<NUM>),
characterized in that the robot system (<NUM>) further comprises an auxiliary power supply (<NUM>) configured to supply electric power to the non-excitation actuated electromagnetic brake (<NUM>) when the non-excitation actuated electromagnetic brake (<NUM>) is not supplied with electric power from a main power supply (<NUM>) of the robot (<NUM>).