Position detection system, actuator and position detection method

Abstract

A position sensing system (1) comprising a primary encoder (15) that detects the position of a motor shaft of a motor (10) and a secondary encoder (25) that detects the position of an output shaft of a reduction gear (20). The position sensing system (1) further comprises encoder power sources (8, 9) that switch on and operate the primary encoder and / or the secondary encoder in a predetermined situation.

Description

TECHNICAL FIELD

[0001] The present invention relates to a position detection system, an actuator and a method for position detection. STATE OF THE ART

[0002] Actuators consist of a servomotor and a reduction gear connected to each other. A primary encoder is connected to a motor shaft of the servomotor to detect an absolute position within one revolution of the motor shaft and the total number of revolutions of the motor shaft. Similarly, a secondary encoder is connected to an output shaft of the reduction gear to detect an absolute position within one revolution of the output shaft and the total number of revolutions of the output shaft (see JP2007113932A). The information detected by each encoder is stored in a memory.

[0003] In certain situations, such as when the servo motor stops and the reducer output shaft rotates due to inertia, the total number of revolutions of the primary encoder can be determined from the absolute position data of the secondary encoder, as long as the reducer output shaft rotates within one revolution. In this case, any encoder can be used for continuous operation without the need for an additional battery. [CITATION LIST][PATENT LITERATURE]

[0004] PTL 1: JP2007113932A SUMMARY OF THE INVENTION [TECHNICAL PROBLEM]

[0005] The actuator described above can be installed in a specific machine, such as a robot, that has a shaft that can rotate between ±360° and ±720° (between one and two revolutions). If the shaft rotates between one and two revolutions, an additional battery must be provided to continue using each encoder.

[0006] What is desired is an encoder that can be used continuously over the entire range of motion of a shaft without the need for an additional battery. [SOLVING THE PROBLEM]

[0007] According to a first aspect of the present invention, there is provided a position detection system comprising a motor mounted in a machine, a reduction gear coupled to the motor, a primary encoder for detecting a position of a motor shaft of the motor, and a secondary encoder for detecting a position of an output shaft of the reduction gear, and further comprising an encoder power source for switching on and operating the primary encoder and / or the secondary encoder in a predetermined situation.

[0008] According to a further aspect of the present invention, an actuator is provided which comprises a motor, a reduction gear coupled to the motor, a primary encoder for detecting a position of a motor shaft of the motor and a secondary encoder for detecting a position of an output shaft of the reduction gear, and which further comprises an encoder power source for switching on and operating the primary encoder and / or the secondary encoder in a predetermined situation.

[0009] According to another aspect of the present invention, there is provided a position sensing method for a position sensing system comprising a primary encoder for sensing a position of a motor shaft of a motor and a secondary encoder for sensing a position of an output shaft of a reduction gear coupled to the motor, the method comprising the steps of: interrupting power to the motor in response to a stop command for a machine wherein a rotor of the motor rotates due to inertia, switching on and operating the primary encoder and / or the secondary encoder using an encoder power source, and storing the position of the primary encoder and / or the secondary encoder when the output shaft is at a standstill.

[0010] The object, features and advantages of the present invention will become apparent from the following description of the embodiments taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic side view of a position detection system based on a first and a second embodiment of the present invention. Fig. 2 is a flowchart showing the operation of the position detecting system based on the first embodiment. Fig. 3 is a flowchart showing the operation of the position detecting system based on the second embodiment. Fig. Figure 4 is a view showing the relationship between time and the position of the output shaft of a reduction gear. DESCRIPTION OF THE EMBODIMENTS

[0011] The embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, corresponding components are designated by the same reference numerals.

[0012] Fig. 1 is a schematic side view of a position detection system based on a first embodiment of the present invention. The position detection system 5 is incorporated into a machine 3 having a shaft, such as a robot 3. Although the case where the position detection system 5 is incorporated into the robot 3 will be described below, the same applies to the case where the position detection system 5 is incorporated into another machine 3 having a shaft, such as a machine tool.

[0013] In Fig. 1, an actuator 6 arranged in a link 1 comprises a motor 10, e.g., a servomotor, and a reduction gear 20 coupled to a motor shaft 13 of the motor 10, which are connected to each other. The motor 10 comprises a rotor 12 that rotates together with the motor shaft 13, and a stator 11 arranged to surround the rotor 12. The end face of an output shaft 23 of the reduction gear 20 is connected to a link 2. In this way, the actuator 6, formed from the motor 10 and the reduction gear 20, rotates the link 2 relative to the link 1 within a predetermined operating range to determine its positioning. The reduction ratio of the reduction gear 20 is, for example, 1:50.

[0014] The motor shaft 13 is, for example, a hollow shaft, with a primary encoder 15 attached to its rear end. The primary encoder 15 is, for example, an incremental encoder and outputs A-phase, B-phase, and Z-phase signals. The output signals are detected by a detection unit 16, which detects an absolute position PA1 within one revolution of the motor shaft 13 and a total number of revolutions PB1 using a known method. The detected information is stored in a memory 7, e.g., a temporary memory.

[0015] The output shaft 23 extends through the hollow motor shaft 13 toward the side of the motor 10, and a secondary encoder 25 is arranged at a rear end of the output shaft 23. The secondary encoder 25 is, for example, an incremental encoder and outputs A-phase, B-phase, and Z-phase signals. The output signals are detected by a detection unit 26, which detects an absolute position PA2 within one revolution of the output shaft 23 and a total number of revolutions PB2 according to a known method. The detected information is stored in a memory 7, e.g., a temporary memory. The primary encoder 15 and the secondary encoder 25 are known to consist of the respective rotary disks 15A, 25A.

[0016] The information stored in the memory 7 can be stored for a certain period of time thanks to a battery 8, e.g. a button battery or a capacitor. Fig. The position detection system 5 shown in Figure 1 comprises a common memory 7 and a common battery 8 for the primary encoder 15 and the secondary encoder 25. However, the primary encoder 15 and the secondary encoder 25 may each comprise their own memory and battery.

[0017] The information stored in memory 7 is transmitted to a controller 9 for controlling machine 3. Controller 9 may be an LSI arranged at encoders 15 and 25. Based on the transmitted information, controller 9 drives and controls motor 10 and performs a positioning operation to position link 2 in a target position relative to link 1. Furthermore, a brake mechanism 50 arranged on the outer surface of motor shaft 13 is actuated in response to a command from controller 9 to stop motor shaft 13. Furthermore, controller 9 also serves to turn on primary encoder 15 and secondary encoder 25 during operation of machine 3 with links 1 and 2.

[0018] Fig. Figure 2 is a flowchart showing the operation of the position detection system based on the first embodiment. Fig. The contents shown in Figure 2 are implemented, for example, when the machine 3, e.g., a robot 3 operating in accordance with operating commands, stops due to a certain cause and it is necessary to resume the operation of the machine 3. The program relating to the Fig. 2 is stored in a storage unit (not shown) connected to the control unit 9. The following describes the case where the machine 3 is a robot 3, but the same applies when the machine 3 is a machine tool or the like.

[0019] First, in step S11, the robot 3 is stopped due to a specific cause, such as when the robot 3 comes into contact with a foreign object. For safety reasons, the built-in brake mechanism 50 is then automatically activated to stop the motor shaft 13. Furthermore, the controller 9 cuts off the power supply to the motor 10, the primary encoder 15, and the secondary encoder 25. As a result, the joints of the robot 3 become immobile.

[0020] Next, in step S12, the operator actuates the built-in brake mechanism 50 to allow the motor shaft 13 to rotate. The operator then begins to manually operate the robot 3 (step S13). At the same time, an encoder power source, e.g., the control unit 9, begins to supply power to the primary encoder 15 and / or the secondary encoder 25 (step S14).

[0021] In other words, in the first embodiment, in a given situation, specifically when the robot 3 stops and the brake mechanism 50 is actuated, an encoder power source, e.g., the controller 9, begins to supply power to the primary encoder 15 and / or the secondary encoder 25. As a result, the powered-on encoders 15, 25 continue to detect the absolute positions PA1, PA2 and the total rotational speeds PB1, PB2 (step S15).

[0022] Subsequently, in step S16, when the robot 3 is sufficiently away from the foreign object, for example, and the specific cause described above has been eliminated, the operator manually stops the robot 3. When the robot 3 is stopped, the absolute positions PA1, PA2 and the total revolutions PB1, PB2 are stored in the memory 7, and the power supply from the encoder power source, e.g., the controller 9, to the primary encoder 15 and / or the secondary encoder 25 is interrupted (step S17). In step S18, the built-in brake mechanism 50 is applied again to prevent the motor shaft 13 from rotating. As a result, the robot 3 is in the same state as when the robot 3 was stopped in step S1.

[0023] Next, in step S19, it is determined whether or not there are any operating commands for the robot 3. If there are no operating commands, the system waits until an operating command is received. If an operating command is present, the system proceeds to step S20, in which the built-in brake mechanism 50 is actuated again. This causes the motor shaft 13 to rotate. In step S21, the controller 9 reads the absolute positions PA1, PA2 and the total rotational speeds PB1, PB2 stored in the memory 7. The controller 9 then resumes operation of the robot 3 according to the operating commands received in step S19 (step S22).

[0024] As described above, in the first embodiment, after step S12, a situation occurs in which the robot 3 stops and the brake mechanism 50 is actuated. In this situation, the controller 9, which serves as the encoder power source, causes the primary encoder 15 and / or the secondary encoder 25 to continue detecting positions and stores the results in the memory 7 (steps S15 and S17). The contents of the memory 7 are then read, and the operation of the machine 3 is resumed (steps 21 and 22).

[0025] Thus, in the first embodiment, even when the output shaft 23 rotates one to two revolutions, the secondary encoder 25 can be used continuously over the entire range of motion of the output shaft 23 without requiring an additional battery. Specifically, in the first embodiment of the present invention, it is possible to provide a position detection system 1 that can be used continuously over the entire range of motion of the output shaft 23 without a battery. It should be noted that the primary encoder 15 can also be used continuously over the entire range of motion of the output shaft 23.

[0026] Fig. 3 is a flowchart showing the operation of the position detection system based on the second embodiment. Fig. The contents shown in Figure 3 are implemented when the machine 3, e.g., the robot 3, performs an emergency stop during operation. The operating program related to the Fig. 3 is stored in a storage unit (not shown) connected to the control unit 9. The following describes the case where the machine 3 is a robot 3, but the same applies if the machine 3 is a machine tool or the like.

[0027] First, in step S31, robot 3 operates according to its operating program. In step S32, it is determined whether or not an emergency stop command has been issued to robot 3, and the operation of robot 3 continues as long as no stop command is issued. If a stop command has been issued, the process proceeds to step S33.

[0028] When the stop command is issued, the power supply to the robot 3 is interrupted by the controller 9 (step S33). Specifically, the controller 9 stops the power supply to the motor 10, the primary encoder 15, and the secondary encoder 25. As a result, the joints of the robot 3 stop moving. Although the motor 10 is stopped at this time, the output shaft 23 of the reduction gear 20 continues to move due to inertia (step S34).

[0029] Fig. Figure 4 is a view showing the relationship between time and the position of the output shaft of the reduction gear. Fig. 4, the horizontal axis represents time and the vertical axis represents the position of the output shaft 23 of the reduction gear 20. As in Fig. 4, the position of the output shaft 23 continues to change even if the robot 3 is stopped by a stop signal, since the output shaft 23 rotates due to its inertia.

[0030] In step S35, the backup battery 8 serving as the encoder power source supplies power not only to the memory 7 but also to the primary encoder 15 and / or the secondary encoder 25.

[0031] In other words, in the second embodiment, in a given situation, specifically, in a situation where the output shaft 23 rotates due to inertia because the power supply to the motor 10 has been stopped, an encoder power source, such as the battery 8, starts supplying power to the primary encoder 15 and / or the secondary encoder 25. As a result, the powered-on encoders 15, 25 continue to detect the absolute positions PA1, PA2 and the total rotational speeds PB1, PB2 (step S35).

[0032] As from Fig. As can be seen from Figure 4, the output shaft 23, which rotates due to its inertia, stops after rotating for a certain period of time. If it is confirmed in step S36 that the output shaft 23 has stopped, the process proceeds to step S37, in which the absolute positions PA1, PA2 and the total rotational speeds PB1, PB2 are stored in the memory 7 (step S37).

[0033] Thus, in the second embodiment, after step S33, a situation arises in which the output shaft 23 rotates due to inertia because the power supply to the motor 10 has been interrupted. Position detection of the primary encoder 15 and / or the secondary encoder 25 is continued by the backup battery 8 as the encoder power source, and the results are stored in the memory 7 (steps S35, S37). The contents of the memory 7 are then read, and operation of the machine 3 is resumed (steps 40, 41).

[0034] Thus, in the second embodiment, after step S33, a situation occurs in which the output shaft 23 rotates due to inertia because the power supply to the motor 10 has been interrupted. Position detection of the primary encoder 15 and / or the secondary encoder 25 continues using the battery 8 as the encoder power source, and the results are stored in the memory 7 (steps S35, S37). The contents of the memory 7 are then read, and operation of the machine 3 is resumed (steps 40, 41).

[0035] Therefore, in the second embodiment, even when the output shaft 23 rotates one to two revolutions, the secondary encoder 25 can be used continuously over the entire range of motion of the output shaft 23 without requiring an additional battery. Specifically, in the second embodiment of the present invention, it is possible to provide a position detection system 1 that can be used continuously over the entire range of motion of the output shaft 23 without a battery. The primary encoder 15 can also be used continuously over the entire range of motion of the output shaft 23.

[0036] In the first and second embodiments, no additional power source or the like is required because the encoder power source is the controller 9 or the battery 8 of the position detection system 1. The encoder power source (controller 9, battery 8) supplies power to the primary encoder 15 and / or the secondary encoder 25 in the predetermined situation described above. However, the encoder power source (controller 9, battery 8) may also supply power only to the secondary encoder 25 in the predetermined situation described above. In this case, the total number of revolutions PB1 of the primary encoder 15 can be determined based on the absolute position PA2 and the total number of revolutions PB2 of the secondary encoder 25, and the absolute position PA1 can be calculated. It can therefore be seen that less power is required for the encoder power source. Such a case also falls within the scope of the present invention. ASPECTS OF THE PRESENT INVENTION

[0037] According to a first aspect, a position sensing system is provided comprising a primary encoder for detecting a position of a motor shaft of a motor and a secondary encoder for detecting a position of an output shaft of a reduction gear coupled to the motor, and further comprising an encoder power source for switching on and operating the primary encoder and / or the secondary encoder in a predetermined situation.

[0038] According to a second aspect, in the first aspect, the predetermined situation is a situation in which a machine is stopped and a brake mechanism is actuated to stop the motor shaft of the motor and / or the output shaft of the reduction gear.

[0039] According to a third aspect, in the second aspect, the encoder power source is a control device for controlling the machine.

[0040] According to a fourth aspect, in the first aspect, the predetermined situation is a situation in which the output shaft rotates due to inertia after the power supply to the motor is interrupted.

[0041] According to a fifth aspect, in the fourth aspect, the power source of the encoder is a capacitor or a backup battery.

[0042] According to a sixth aspect of the first aspect, the encoder power source is configured to supply power only to the secondary encoder.

[0043] According to a seventh aspect, an actuator is provided comprising a motor, a reduction gear coupled to the motor, a primary encoder for detecting a position of a motor shaft of the motor, and a secondary encoder for detecting a position of an output shaft of the reduction gear, and further comprising an encoder power source for switching on and operating the primary encoder and / or the secondary encoder in a predetermined situation.

[0044] According to an eighth aspect, in the seventh aspect, the predetermined situation is a situation in which a machine is stopped and a brake mechanism is operated to stop the motor shaft of the motor and / or the output shaft of the reduction gear.

[0045] According to a ninth aspect, in the eighth aspect, the power source for the encoder is a control device for controlling the machine.

[0046] According to a tenth aspect, the seventh aspect, the predetermined situation is a situation in which the output shaft rotates due to inertia after the power supply to the motor is interrupted.

[0047] According to an eleventh aspect, in the tenth aspect, the power source of the encoder is a capacitor or a backup battery.

[0048] According to a twelfth aspect, in the seventh aspect, the encoder power source is configured to supply power only to the secondary encoder.

[0049] According to a thirteenth aspect, a position sensing method is provided for a position sensing system comprising a primary encoder for sensing a position of a motor shaft of a motor and a secondary encoder for sensing a position of an output shaft of a reduction gear coupled to the motor, the method comprising the steps of: interrupting power to the motor in response to a stop command for a machine, a rotor of the motor rotating due to inertia, switching on and operating the primary encoder and / or the secondary encoder using an encoder power source, and storing the position of the primary encoder and / or the secondary encoder when the output shaft is at a standstill.

[0050] According to a fourteenth aspect, in the thirteenth aspect, the power source of the encoder is a capacitor or a backup battery.

[0051] Although the embodiments of the present invention have been described in detail, the present invention is not limited to the individual embodiments described above. Various additions, replacements, changes, or partial deletions may be made to these embodiments within the spirit of the invention or within the scope of the idea and intent of the present invention, which can be understood from the contents described in the claims and their subjects. For example, the order of each operation and the order of each method of the above-described embodiments are presented as examples and are not limited to them. The same applies when numerical values ​​or formulas are used in the description of the above-described embodiments. Furthermore, suitable combinations of some of the above-described embodiments are included within the scope of the present invention.

[0052] Although the embodiments of the present invention are described above, it should be understood by those skilled in the art that various modifications and changes can be made without departing from the scope of the claims described below. LIST OF REFERENCE SYMBOLS 1 position detection system 3 Machine (robot) 5 Position detection system 6 Actuator 7 storage 8 Battery (encoder power source) 9 Control unit (encoder power source) 10 Engine 11 Stator 12 Rotor 13 Motor shaft 15 primary encoder 16 Recording unit 20 reduction gears 23 Output shaft 25 secondary encoder 26 Detection unit 50 Brake mechanism QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2007113932A [0002, 0004]

Claims

[1] Position detection system, comprising: a primary encoder for detecting a position of a motor shaft of a motor, and a secondary encoder for detecting a position of an output shaft of a reduction gear coupled to the motor, and further comprising: an encoder power source for switching on and operating the primary encoder and / or the secondary encoder in a given situation. [2] A position detecting system according to claim 1, wherein the predetermined situation is a situation in which a machine is stopped and a brake mechanism is operated to stop the motor shaft of the motor and / or the output shaft of the reduction gear. [3] Position detection system according to claim 2, wherein the encoder power source is a controller for controlling the machine. [4] A position detecting system according to claim 1, wherein the predetermined situation is a situation in which the output shaft rotates due to inertia after the power supply to the motor is interrupted. [5] The position detection system of claim 4, wherein the encoder power source is a capacitor or a backup battery. [6] The position sensing system of claim 1, wherein the encoder power source is configured to power only the secondary encoder. [7] Actuator comprising: an engine, a reduction gear coupled to the motor, a primary encoder for detecting a position of a motor shaft of the motor, and a secondary encoder for detecting a position of an output shaft of the reduction gear, and further comprising: an encoder power source for switching on and operating the primary encoder and / or the secondary encoder in a given situation. [8] An actuator according to claim 7, wherein the predetermined situation is a situation in which a machine is stopped and a brake mechanism is operated to stop the motor shaft of the motor and / or the output shaft of the reduction gear. [9] Actuator according to claim 8, wherein the encoder power source is a control device for controlling the machine. [10] The actuator according to claim 7, wherein the predetermined situation is a situation in which the output shaft rotates due to inertia after the power supply to the motor is interrupted. [11] The actuator of claim 10, wherein the encoder power source is a capacitor or a backup battery. [12] The actuator of claim 7, wherein the encoder power source is configured to power only the secondary encoder. [13] A position detection method for a position detection system comprising a primary encoder for detecting a position of a motor shaft of a motor and a secondary encoder for detecting a position of an output shaft of a reduction gear coupled to the motor, the method comprising the following steps: Interrupting the power supply to the motor in response to a stop command for a machine, whereby a rotor of the motor rotates due to inertia, Switching on and operating the primary encoder and / or the secondary encoder using an encoder power source, and Saving the position of the primary encoder and / or the secondary encoder when the output shaft is at a standstill. [14] A position detection method according to claim 13, wherein the encoder power source is a capacitor or a backup battery.

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