# US 11,307,057 B2 · Encoder abnormality detection method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,307,057 B2 - Document ID: US11307057B2 - Status: Granted - Kind: B2 - Application number: 16/780,875 - Filed: 2020-02-03 - Published: 2020-06-04 - Granted: 2022-04-19 - Earliest claimed: 2017-08-08 - Assignees: Panasonic Intellectual Property Management Co., Ltd. - Applicants: Panasonic Intellectual Property Management Co., Ltd. - Inventors: Yasuhiro Kinugasa - Web page: https://patentgrep.com/patent/US11307057B2 ## CPC - G01D 3/08: with provision for safeguarding the apparatus, e.g. against abnormal operation, against breakdown - G01D 5/24466: {Comparison of the error value to a threshold} - B25J 15/02: servo-actuated - B25J 19/06: Safety devices - G05B 9/02: electric - G05D 3/12: using feedback - H02P 29/024: Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load - G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR - B25J: MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES ({manipulators specially adapted for use in surgery A61B34/70; manipulators used in cleaning hollow articles B08B9/04}; manipulators associated with rolling mills B21B39/20; manipulators associated with forging machines B21J13/10; {manipulators associated with picking-up and placing mechanisms B23P19/007}; means for holding wheels or parts thereof B60B30/00; {vehicles with ground-engaging propulsion means, e.g. walking members B62D57/02, B62D57/032; devices for picking-up and depositing articles or materials between conveyors B65G47/90, B65G47/91; manipulators with gripping or holding means for transferring packages B65H67/065}; cranes B66C; {manipulators used in the protection or supervision of pipe-line installations F17D5/00; walking equipment adapted for nuclear steam-generators F22B37/006}; manipulators specially adapted for, or associated with, nuclear reactors G21C; {apparatus used for handling wafers during manufacture or treatment of semiconductor H10P72/50}) - G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G) - G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS ## Abstract In a robot including a motor and an encoder for detecting the rotational position of the motor, the controller outputs a speed command indicating the rotational position of the motor and sends commanded-position information indicating the rotational position of the motor according to the speed command to a safety unit for detecting a fault in the encoder. When the controller is holding modified point-of-origin information of the motor and the safety unit is holding the original point-of-origin information, the controller sends commanded-position information generated based on the original point-of-origin information to the safety unit. ## Claims ### Claim 1 A method for detecting a fault in an encoder, the encoder being configured to detect a rotational position of a motor, the motor being configured to drive an output shaft of an operating device, the operating device including: a fault detection unit configured to detect the fault in the encoder; a controller configured to output a speed command indicating the rotational position of the motor and to send to the fault detection unit commanded-position information indicating the rotational position of the motor according to the speed command; and a driver configured to receive the speed command from the controller and an output signal from the encoder and to control driving of the motor based on the speed command and the output signal, the method comprising: an information transmission step of causing the controller to send to the fault detection unit the commanded-position information, the commanded-position information being compensated for a time delay due to a delay in drive control of the motor; an information acquisition step of causing the fault detection unit to receive the commanded-position information from the controller and the output signal from the encoder; and a fault determination step of causing the fault detection unit to compare the commanded-position information compensated for the time delay and detected-position information of the motor calculated based on the output signal and to determine that the encoder is faulty when there is a difference of not less than a predetermined value between the commanded-position information compensated for the time delay and the output signal, wherein in the fault determination step, a presence or absence of the fault in the encoder determined by the fault detection unit is based on a comparison result between the detected-position information and a sum of the commanded-position information and an integrated value of an amount of change of the commanded-position information. ### Claim 2 (depends on 1) The method according to claim 1, wherein in the information transmission step, the commanded-position information sent from the controller to the fault detection unit does not contain a resonant component, and in the fault determination step, a presence or absence of the fault in the encoder determined by the fault detection unit is based on a comparison result between the detected-position information and the commanded-position information from which the resonant component has been removed. ### Claim 3 (depends on 1) The method according to claim 1, wherein in the information transmission step, when the controller is holding modified point-of-origin information of the motor and the fault detection unit is holding original point-of-origin information of the motor, the commanded-position information sent from the controller to the fault detection unit is based on the original point-of-origin information, and in the fault determination step, a presence or absence of the fault in the encoder determined by the fault detection unit is based on the comparison result between the detected-position information and the commanded-position information generated based on the original point-of-origin information. ### Claim 4 (depends on 1) The method according to claim 1, wherein in the fault determination step, the presence or absence of the fault in the encoder determined by the fault detection unit is based on a comparison result between the detected-position information and a value obtained by adding a predetermined threshold to the sum of the integrated value and the commanded-position information. ### Claim 5 (depends on 1) The method according to claim 1, wherein the operating device further includes a safety circuit configured to emergency-stop the operating device, the controller is configured to send the safety circuit an emergency stop signal in case of an emergency, and in the fault determination step, when detecting the emergency stop signal sent from the controller, the fault detection unit does not determine that the encoder is faulty even if the difference between the commanded-position information and the output signal is not less than the predetermined value. ### Claim 6 (depends on 1) The method according to claim 1, wherein the operating device is a robot. ### Claim 7 A method for detecting a fault in an encoder, the encoder being configured to detect a rotational position of a motor, the motor being configured to drive an output shaft of an operating device, the operating device including: a fault detection unit configured to detect the fault in the encoder; a controller configured to output a speed command indicating the rotational position of the motor and to send to the fault detection unit commanded-position information indicating the rotational position of the motor according to the speed command; and a driver configured to receive the speed command from the controller and an output signal from the encoder and to control driving of the motor based on the speed command and the output signal, the method comprising: an information transmission step of causing the controller to send to the fault detection unit the commanded-position information, the commanded-position information being compensated for a time delay due to a delay in drive control of the motor; an information acquisition step of causing the fault detection unit to receive the commanded-position information from the controller and the output signal from the encoder; and a fault determination step of causing the fault detection unit to compare the commanded-position information compensated for the time delay and detected-position information of the motor calculated based on the output signal and to determine that the encoder is faulty when there is a difference of not less than a predetermined value between the commanded-position information compensated for the time delay and the output signal, wherein the operating device further includes a safety circuit configured to emergency-stop the operating device, the controller is configured to send the safety circuit an emergency stop signal in case of an emergency, and in the fault determination step, when detecting the emergency stop signal sent from the controller, the fault detection unit does not determine that the encoder is faulty even if the difference between the commanded-position information and the output signal is not less than the predetermined value.