Manipulator system

A manipulator system includes arithmetic logic units for calculating an operation quantity per unit time of a power source mounted on a surgical instrument as a first operation quantity and calculating an operation quantity per unit time of the power source as a second operation quantity. A determining unit is used for outputting a shutoff signal for de-energizing the power source if the first operation quantity is smaller than a first threshold value and the second operation quantity is larger than a second threshold value. A cutoff unit is configured to cut off the drive signal output from the output unit to the power source in response to the shutoff signal output for de-energizing the power source from the determining unit.

TECHNICAL FIELD

The technology disclosed herein relates to a manipulator system.

DESCRIPTION OF THE RELATED ART

There have been known medical manipulators for treating a tissue in a body of a patient under remote control. Generally, the medical manipulators have a safety device for preventing them from malfunctioning due to a failure of parts that make up the manipulators. For example, Japanese Patent JP 2013-094452A discloses a surgery supporting apparatus having a controller for detecting a failure of one surgical instrument mounted on a manipulator using a plurality of encoders provided on the surgical instrument. The surgery supporting apparatus revealed in JP 2013-0944521 calculates a difference between operation quantities of the surgical instrument that are detected by the encoders. The surgery supporting apparatus compares the difference with a predetermined threshold value to detect a failure of at least one of the encoders. Upon detection of the failure of the encoder, the surgery supporting apparatus disclosed in JP 2013-094452 brings the surgical instrument to a secure stop.

According to the technology disclosed in JP 2013-094452, it is determined that there is a failure in an encoder in the event that the difference between the operation quantities detected by the respective encoders increases in excess of the threshold value. The surgical instrument operates despite the failure immediately after the failure occurred in the encoder until the difference exceeds the threshold value. Therefore, in the event of a failure of the transmission of power to the surgical instrument, it is required to shorten the time from the occurrence of the failure to the shutdown of the surgical instrument. Therefore, there is a need for a manipulator system that can be safely operated in the event of the failure of the transmission of power to the surgical instrument.

BRIEF SUMMARY OF EMBODIMENTS

The technology disclosed herein is directed to a manipulator system capable of making a quick transition to a safe state in the event of a failure of the transmission of power to a surgical instrument thereof.

According to one aspect of the technology disclosed herein, a manipulator system includes a power source, a first sensor, a second sensor, an arithmetic logic unit, an operation input device, a control signal generator, an output unit, a determining unit, and a cutoff unit all of which are directly or indirectly interconnected to one another for treating a tissue in a body of a patient. The power source is configured to generate drive power for operating a surgical instrument. The first sensor is configured to detect a first detected value corresponding to a drive quantity of the power source. The second sensor is configured to detect a second detected value corresponding to the drive quantity of the power source. An arithmetic logic unit is configured to calculate a first operation quantity of the power source per unit time based on the first detected value. The arithmetic logic unit is configured to calculate a second operation quantity of the power source per unit time based on the second detected value. The operation input device is operable by a user for executing an input command. The control signal generator is configured to receive a signal output from the operation input device and generate a control signal for operating the surgical instrument. The output unit is configured to receive the control signal generated by the control signal generator and generate a drive signal for energizing the power source. The determining unit is configured to output a shutoff signal for de-energizing the power source if the first operation quantity is smaller than a first threshold value and the second operation quantity is larger than a second threshold value. The cutoff unit is configured to cut off the drive signal output from the output unit to the power source in response to the shutoff signal output for de-energizing the power source from the determining unit.

The determining unit may output the shutoff signal if the absolute value of the difference between the first operation quantity calculated based on the first detected value and the second operation quantity calculated based on the second detected value is larger than a third threshold value, in the event that the first operation quantity is larger than the first threshold value or the second operation quantity is smaller than the second threshold value. The power source may be detachably attached to the surgical instrument. The power source may be capable of transmitting the drive power to the surgical instrument when the power source is attached to the surgical instrument. The power source may have one or more connect/disconnect sensor configured to output a signal to the determining unit when the surgical instrument and the power source are attached to each other. The determining unit may output the shutoff signal if the signal is input to the determining unit and if the first operation quantity is smaller than the first threshold value and the second operation quantity is larger than the second threshold value. The first threshold value may be equal to or smaller than the second threshold value.

The manipulator system according to the aforementioned aspect may further include an operation unit configured to operate the surgical instrument. The surgical instrument may have an electrode for treating a tissue. The operation unit may have a switch for selectively turning on and off the supply of an electric current to the electrode. The determining unit may output the shutoff signal based on the result of comparison between a third threshold value and the absolute value of the difference between (i) the operation quantity calculated based on the first detected value and (ii) the operation quantity calculated based on the second detected value, in the event that the supply of an electric current to the electrode is turned off. The determining unit may output the shutoff signal if (i) the first operation quantity is smaller than the first threshold value and (ii) the second operation quantity is larger than the second threshold value, in the event that the supply of an electric current to the electrode is turned on.

According to another aspect of the technology disclosed herein, a manipulator system includes an elongated member, an operation input device, a drive unit, a transmitted member, a first sensor, a second sensor, and at least one manipulator control device. The elongated member includes at least one joint. The operation input device is operable by a user for entering an input. The drive unit is configured to output drive power for actuating the joint in response to the input from the operation input device. The drive power is transmitted from the drive unit to the transmitted member. The transmitted member is rotatable by the drive power. The first sensor is configured to be mounted on the drive unit. The first sensor is configured to detect over time an angular displacement of the drive unit when the drive unit actuates the joint. The first sensor is configured to output a first detected value representing the detected angular displacement. The second sensor is configured to be mounted on the transmitted member. The second sensor is configured to detect over time an angular displacement of the transmitted member when the drive unit actuates the joint. The second sensor is configured to output a second detected value representing the detected angular displacement. The at least one manipulator control device is configured to calculate a first difference and a second difference. The first difference represents an amount of change in the angular displacement with respect to time change based on the first detected value. The second difference represents an amount of change in the angular displacement with respect to time change based on the second detected value. The at least one manipulator control device compares the first difference and a first threshold value with one another and compares the second difference and a second threshold value with another. The at least one manipulator control device controls the drive unit to de-energize the drive unit if the first difference is smaller than the first threshold value and the second difference is larger than the second threshold value. Accordingly, the manipulator system disclosed herein is capable of making a quick transition to a safe state in the event of a failure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, various embodiments of the technology will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the technology disclosed herein may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiment being described.

A first embodiment is described hereinafter with reference toFIGS. 1 through 11in whichFIG. 1is a general view of the manipulator system according to the present embodiment.

The manipulator system1, includes an operation input device2, a manipulator5, and a manipulator control device30all of which are directly or indirectly connected to one another to operate on a body of a patient. An operation input command is applied by a user to the operation input device2. The manipulator5performs a treatment or the like in the body of the patient according to an operation input command applied to the operation input device2. The manipulator control device30controls the manipulator5to operate according to an operation input command applied to the operation input device2. The operation input device2functions as a master for transmitting an operation movement of the user, e.g., a surgeon, to the manipulator5. The operation input device2includes a display unit3and an operation unit4. The display unit3includes a monitor3aand a monitor3b. The monitor3adisplays a video image of a surgical region of the patient and its neighborhood which is captured by a laparoscope100. The monitor3bdisplays an error message, and the like issued by the manipulator system1. The operation unit4is connected to the manipulator control device30for communication therewith so that the operation unit4can transmit an operation movement of the user to the manipulator5. When the operation unit4is operated by the user, the operation unit4outputs an operation signal to the manipulator control device30for actuating the manipulator5in accordance with the movement of the user who operates the operation unit4. The manipulator5includes a plurality of surgical instruments6and drive units22for moving the respective surgical instruments6. The surgical instruments6are controlled for their movements based on control signals output from the manipulator control device30.

FIG. 2is a schematic view depicting each of the surgical instruments6of the manipulator system1. Each surgical instrument6includes an insert7and a driven unit15. The insert7is attached to a driven unit15and is inserted into the body of patient. The driven unit15is connected to a drive unit22. One or more of the surgical instruments6have a high-frequency treatment instrument6A for performing a high-frequency treatment. The high-frequency treatment instrument6A is connected to a high-frequency power supply60that can be operated by a foot switch61for energization with a high-frequency current. The insert7is shaped like an elongated shank. When the insert7is in use, one end that is on a side of the treatment unit8is directed toward the body of the patient. For clarity purpose, for indicating relative axial positions on the insert7, those closer to the treatment unit8is referred to as those on a distal-end side, whereas those closer to the drive unit22is referred to as those on a proximal-end side, unless otherwise specified. The insert7includes the treatment unit8disposed on the distal-end side to be directed toward the patient and an elongate member10coupled to the treatment unit8. As depicted inFIG. 2, the treatment unit8includes electrodes9for making an incision in a tissue of the patient. For example, the electrodes9of the high-frequency treatment instrument6A are capable of making an incision in a tissue when supplied with a high-frequency current from the high-frequency power supply60. The elongated member10includes a joint11connected to the treatment unit8and a flexible tube12connected to the joint11. In response to the transmission of drive power produced by the drive unit22, the joint11operates to change the orientation of the treatment unit8with respect to the distal end of the flexible tube12. A plurality of joints11are connected to a pulley18of the driven unit15through respective wires (W). Although inFIG. 2one single joint11is illustrated, but one of ordinary skill in the art would appreciate that a plurality of joints11may be provided. According to the present embodiment, the elongated member10is illustrated as having the flexible tube12, however, depending on the construction and the intended use, a hard tube may be used as well. The flexible tube12is a soft tubular member having openings at respective distal and proximal ends. The wire (w) for transmitting drive power from the drive unit22to the joint11is inserted in the flexible tube12.

FIG. 3is a diagram depicting internal structures of the drive unit22and the driven unit15of the manipulator system1. The driven unit15includes a transmitted member or pulley18, that is coupled to an output shaft26of the drive unit22and angularly rotatable by drive power transmitted from the drive unit22. The pulley18has a groove defined in an outer circumferential surface thereof. The wire (w) extends from the proximal end of the flexible tube12and the wire (w) is trained in the outer circumferential surface. Drive power produced by the drive unit22is transmitted to the pulley18. The drive power that is transmitted to the pulley18is transmitted to the wire (w). Therefore, depending on the operation of the drive unit22, the wire (w) is advanced or retracted longitudinally in the flexible tube12, transmitting the drive power produced by the drive unit22to the joint11as depicted inFIG. 2. The manipulator system1includes movable arms21for adjusting the positions and orientations of the surgical instruments6. The arms21support the respective drive units22. The drive unit22includes an electric motor23, a drive unit encoder24, a speed reducer mechanism25, the output shaft26, and a driven unit encoder27. The electric motor23used as a power source electrically connected to the manipulator control device30. The drive unit encoder24is connected to the rotational shaft of the electric motor23. The speed reducer mechanism25is connected to the rotational shaft of the electric motor23. The output shaft26is mounted on the speed reducer mechanism25. The driven unit encoder27is indirectly connected to the output shaft26via a gear28and being capable to actuate by drive power transmitted from a gear28of the drive unit22.

The electric motor23is electrically connected to the manipulator control device30. The electric motor23used as a drive power source producing drive power for actuating the surgical instrument6. The drive unit encoder24used as a sensor or a first sensor, for detecting an operation quantity of the drive unit22. The drive unit encoder24generates a pulse signal, or a first detected value, in tandem with an angular displacement of the rotational shaft of the electric motor23. The electric motor23may be a servomotor or the like including the drive unit encoder24for detecting an operation quantity of the electric motor23. The driven unit encoder27used as a sensor or a second sensor, for detecting an operation quantity of the drive unit22at a site different from the drive unit encoder24. The driven unit encoder27detects an operation quantity of a portion of a power transfer path from the drive unit22to the surgical instrument6. For example, the portion of a power transfer path is the output shaft26of the speed reducer mechanism25in the present embodiment. The driven unit encoder27is connected to the output shaft26through a gear28mounted on the output shaft26of the speed reducer mechanism25. The driven unit encoder27generates a pulse signal, or a second detected value, in tandem with an angular displacement of the output shaft26.

FIG. 4is a block diagram depicting the manipulator control device30of the manipulator system1. The manipulator control device30includes a control signal generator31, an output unit32, a cutoff unit33, a first position calculator34, a first arithmetic logic unit35, a second position calculator40, a second arithmetic logic unit41, a first determining unit46, and a second determining unit47. The control signal generator or a first processor31is connected to the operation input device2. The output unit or a driver32, is connected to the control signal generator31. The cutoff unit or a relay33, is connected to the output unit32. The first position calculator or a second processor34is connected to the drive unit encoder24. The first arithmetic logic unit or a third processor35is connected to the first position calculator34. The second position calculator or a fourth processor40, is connected to the driven unit encoder27. The second arithmetic logic unit or a fifth processor41is connected to the second position calculator40. The first determining unit a sixth processor46or is connected to the first arithmetic logic unit35and the second arithmetic logic unit41. The second determining unit or a seventh processor47is connected to the first position calculator34and the second position calculator40. All of the processors such as first through seventh processors may be constructed as programmable devices such as CPUs, FPGAs, or the like, or devices such as ASICs. All of the processors disclosed herein may be constructed all in one device or may be constructed as respective individual devices. Further alternatively, the first through seventh processors may be divided into groups and/or devices may be assigned to those groups such that, for example, the first processor and seventh processor are constructed as one CPU and the second processor through sixth processor as FPGAs.

An operation signal input is output from the operation input device2to the manipulator control device30. The control signal generator31receives the operation signal input. The control signal generator31generates control signals for moving the manipulator5or the surgical instruments6. The control signal generator31is connected to the first position calculator34and the second position calculator40. Information of drive quantities of the drive unit22are calculated by the first position calculator34and the second position calculator40. The control signal generator31receives information on the drive quantities input thereto. The control signal generator31performs a feedback control process based on the information of the drive quantities of the drive unit22that are calculated by the first position calculator34and/or the second position calculator40. The control signal generator31outputs the generated control signals to the output unit32. The output unit32receives the control signals input thereto that are output from the control signal generator31, and calculates drive signals for actuating the drive unit22based on the control signals. The output unit32outputs the generated drive signals to the cutoff unit33. The cutoff unit or a relay33switches between an ON state and an OFF state according to the determined results from the first determining unit46and the second determining unit47. In ON state, the cutoff unit33outputs the drive signals output from the output unit32to the electric motor23of the drive unit22. In the OFF state, the cutoff unit33cuts off the drive signals output from the output unit32so that they will not be output to the electric motor23of the drive unit22. Immediately after the cutoff unit33is activated until a cutoff signal, or a first cutoff signal or a second cutoff signal, is output from the first determining unit46and the second determining unit47, the drive signals from the output unit32can be output to the electric motor23of the drive unit22.

The first position calculator34receives the pulse signal generated by the drive unit encoder24. The first position calculator34integrates pulse signals from the drive unit encoder24and generates a count value. The first position calculator34calculates a value corresponding to an operation quantity of the electric motor23, hereinafter referred to as a first operation quantity Ca, based on an initial count value (0) and a latest count value. The first operation quantity Ca is output to the first arithmetic logic unit35, the second determining unit47, and the control signal generator31. The second position calculator40receives the pulse signal generated by the driven unit encoder27. The second position calculator40integrates pulse signals from the driven unit encoder27and generates a count value. The second position calculator40calculates a value corresponding to an operation quantity of the electric motor23, hereinafter referred to as a second operation quantity Cb, based on an initial count value (0) and a latest count value. The second operation quantity Cb is output to the second arithmetic logic unit41, the second determining unit47, and the control signal generator31. The second determining unit47compares the absolute value of the difference between the output Ca from the first position calculator and the output Cb from the second position calculator with a predetermined threshold value, hereinafter referred to as a third threshold value R3, to determine a failure. If the second determining unit47determines that there is a failure, then the second determining unit47outputs a cutoff signal, or a second cutoff signal. The third threshold value R3is a positive value that is larger than an allowable error between the first operation quantity Ca and the second operation quantity Cb, and that is as close to 0 as possible. The first determining unit46determines whether the drive unit encoder24is operating normally or not based on output values of the first arithmetic logic unit35and the second arithmetic logic unit41, i.e., performs a failure determination, and outputs a cutoff signal, or a first cutoff signal, if it determines that there is a failure.

FIG. 5is a block diagram depicting the first arithmetic logic unit35of the manipulator control device30. The first operation quantity Ca output from the first position calculator34is input to the first arithmetic logic unit35. The first arithmetic logic unit35includes a position information memory36, a difference arithmetic logic unit37, a reference value memory39, and a comparative arithmetic logic unit38. The position information memory36acquires first operation quantities Ca at predetermined time intervals from the first position calculator34and storing the acquired first operation quantities Ca. The difference arithmetic logic unit37calculates and execute difference between an output from the first position calculator34and an output from the position information memory36. The reference value memory39stores a predetermined reference value, hereinafter referred to as a first threshold value R1. The comparative arithmetic logic unit38compares and outputs an output from the reference value memory39. A first operation quantity Ca acquired at certain time n is expressed as Ca(n). Ca(n) is input to the position information memory36and the difference arithmetic logic unit37at the same time. The position information memory36is capable of storing at least (i) a latest first operation quantity Ca(n) at the time the first operation quantity Ca is acquired and (ii) a first operation quantity Ca(n−1) acquired immediately before the latest first operation quantity Ca(n). At the time Ca(n) is input to the position information memory36, the position information memory36outputs Ca(n−1) that has been input and stored immediately before Ca(n). The difference arithmetic logic unit37calculates the difference between Ca(n) from the first position calculator34and Ca(n−1) from the positional information memory36, hereinafter referred to as a first differential ΔCa, or ΔCa(n) if the difference is of a value at time n. The first differential ΔCa is of a value representing an operation quantity of the drive unit22per unit time based on the pulse signal from the drive unit encoder24. The difference arithmetic logic unit37outputs the first difference ΔCa to the comparative arithmetic logic unit38. The comparative arithmetic logic unit38reads the first threshold value R1from the reference value memory39and compares the absolute value of the first difference ΔCa with the first threshold value R1. The first threshold value R1is a positive value that is larger than an error which can occur to the first difference ΔCa when the mechanism of the drive unit22operates normally, and that is as close to 0 as possible. The first threshold value R1is determined based on the resolution of the drive unit encoder24and drive power transfer characteristics such as a speed reduction ratio, etc. from the electric motor23to the drive unit encoder24.

FIG. 6is a block diagram depicting the second arithmetic logic unit41of the manipulator control device30. The second operation quantity Cb output from the second position calculator40is input to the second arithmetic logic unit41. The second arithmetic logic unit41includes a position information memory42, a differential arithmetic logic unit43, a reference value memory45, and a comparative arithmetic logic unit44. The position information memory42acquires second operation quantities Cb at predetermined time intervals from the second position calculator40and stores the acquired second operation quantities Cb. The difference arithmetic logic unit43calculates and outputs a difference between an output from the second position calculator and an output from the position information memory42. The reference value memory45stores a predetermined reference value, hereinafter referred to as a second threshold value R2. The comparative arithmetic logic unit44compares and outputs an output from the difference arithmetic logic unit43and an output from the reference value memory45. A second operation quantity Cb acquired at certain time n is expressed as Cb(n). Cb(n) is input to the position information memory42and the difference arithmetic logic unit43at the same time. The position information memory42is capable of storing at least (i) a latest second operation quantity Cb(n) at the time the second operation quantity Cb is acquired and (ii) a second operation quantity Cb(n−1) acquired immediately before the latest second operation quantity Cb(n). At the time Cb(n) is input to the position information memory42, the position information memory42outputs Cb(n−1) that has been input and stored immediately before the latest second operation quantity Cb(n). The time at which the second arithmetic logic unit41acquires a second operation quantity Cb(n) is synchronous with the time at which the first arithmetic logic unit35acquires a first operation quantity Ca(n). The difference arithmetic logic unit43calculates the difference between Cb(n) from the second position calculator40and Cb(n−1) from the position information memory42, hereinafter referred to as a second difference ΔCb, or ΔCb(n) if the difference is of a value at time (n). The second difference ΔCb is of a value representing an operation quantity of the drive unit22per unit time based on the pulse signal from the driven unit encoder27. The difference arithmetic logic unit43outputs the second difference ΔCb to the comparative arithmetic logic unit44.

The comparative arithmetic logic unit44reads the second threshold value R2from the reference value memory45and compares the absolute value of the second difference ΔCb with the second threshold value R2. The second threshold value R2is a positive value that is larger than an error which can occur to the second difference ΔCb when the mechanism of the drive unit22operates normally, and that is as close to 0 as possible. The second threshold value R2is determined based on the resolution of the driven unit encoder27and drive power transfer characteristics such as a speed reduction ratio, etc. from the electric motor23to the driven unit encoder27. If the absolute value of the first difference ΔCa is smaller than the first threshold value R1and the absolute value of the second difference ΔCb exceeds the second threshold value R2, then the first determining unit46outputs a first cutoff signal to the cutoff unit33. The first cutoff signal switches the cutoff unit33to the OFF state to cut off a drive current. The first cutoff signal is a shutoff signal for cutting off a drive signal to the electric motor23. The principle of a failure determination by the first determining unit46will be described hereinafter with reference toFIGS. 7 through 9.FIGS. 7 through 9represent graphs depicting time-depending changes in (i) the operation quantity of the electric motor upon operation of the manipulator control device, (ii) the first and second operation quantities Ca and Cb, (iii) the absolute value |Ca−Cb| of the difference between the first and second operation quantities, and (iV) the absolute values |ΔCa|, |ΔCb| of the first and second differences.

According to the present embodiment, as depicted inFIG. 3, (i) a power transfer path from the electric motor23to the drive unit encoder24and (ii) a power transfer path from the electric motor23to the driven unit encoder27are power transfer paths in which they are mechanically coupled to each other and operate in interlocked relation. The power transfer path from the electric motor23to the drive unit encoder24and the power transfer path from the electric motor23to the driven unit encoder27have respective inherent backlashes. Since the drive unit encoder24is directly mounted on the shaft of the electric motor23, the backlash is so small that it can be ignored. On the other hand, since the driven unit encoder27receives power from the electric motor23through the speed reducer mechanism25and the gear28, the backlash is noticeable. When the electric motor23is operating in one direction beyond a dead zone due to the backlashes after it has started to operate, the drive unit encoder24and the driven unit encoder27are interlocked with each other highly accurately. The principle of a failure determination by the second determining unit47will be described below with reference toFIGS. 7 through 9.FIG. 7depicts changes in the values in case the drive unit22, i.e., the drive unit encoder24and the driven unit encoder27, is operating normally. The first operation quantity Ca that is calculated based on the output from the drive unit encoder24represents essentially the same as the operation quantity of the electric motor23because there is almost no backlash. In the graph depicted inFIG. 7, a curve representing the operation quantity of the electric motor23and a curve representing the first operation quantity Ca are illustrated as essentially overlapping each other. On the other hand, the second operation quantity Cb that is calculated based on the output from the driven unit encoder27starts increasing at a time that lags by T0behind the time at which the electric motor23starts to operate due to the backlashes, and then is linked with the operation of the electric motor23. The absolute value |Ca−Cb| of the difference between the first operation quantity and the second operation quantity, which is calculated by the second determining unit47, increases in unison with Ca as Ca increases until T0and Cb remains 0. After T0, Cb increases similarly to Ca, and hence |Ca−Cb| does not increase anymore, or |Ca−Cb| remains essentially constant. The value |Ca−Cb| at T0defines as the third threshold value R3referred to above. If either the drive unit encoder24or the driven unit encoder27fails and outputs no pulses, then since the difference between Ca and Cb becomes larger, the failure can be detected. On the other hand, if |Ca−Cb| increases but does not exceed R3, then the backlashes may be responsible though there may be a possible failure. If the electric motor23operates repeatedly in normal and reverse directions, then |Ca−Cb| is of a value other than zero (0), and the value is equal to or smaller than R3, under the influence of the backlashes. The drive unit encoder24and the driven unit encoder27operate normally and |Ca−Cb| is essentially constant at R3. Consequently, in order to prevent an erroneous determination, a threshold value larger than R3inFIG. 7has to be use.

FIG. 8depicts changes in the values in case the drive unit encoder24fails at the time the drive unit22starts operating. Since the drive unit encoder24fails and outputs no pulses, the first operation quantity Ca that is calculated based on the output of the drive unit encoder24remains zero (0). On the other hand, the second operation quantity Cb that is calculated based on the output of the driven unit encoder27starts increasing at a time that lags behind the time at which the electric motor23starts to operate, and then is linked with the operation of the electric motor23, in the same manner as if the drive unit encoder24operates normally. The |Ca−Cb| remains zero (0) as both Ca and Cb are zero (0) up to a dead zone T0, not depicted, due to the backlashes. After T0, Cb increases but Ca remains zero (0), so that |Ca−Cb|=Cb. In the graph depicted inFIG. 8, a curve representing the |Ca−Cb| and a curve representing Cb are illustrated as overlapping each other. The |Ca−Cb| continues to increase until it exceeds R3, whereupon the occurrence of a failure is detected. The determination in this case requires a time up to T2until a failure that has occurred is detected.

FIG. 9depicts changes in the values in case the drive unit encoder24fails at time T5(>T0) while the drive unit22is operating. Until T5, the drive unit22operates in the same manner as if it operates normally, and the |Ca−Cb| continues to increase until T0, not depicted, and then is of a constant value after T0. Thereafter, when the drive unit encoder24stops outputting pulses at T5, Ca stops increasing, and only Cb increases. If the |Ca−Cb| that has become large, then starts decreasing. Cb continues to increase to a value that is the same as Ca, whereupon the |Ca−Cb| changes to increase. A failure of the drive unit encoder24is determined when the |Ca−Cb| subsequently exceeds R3. The determination in this case requires a time T7-T5until a failure that has occurred is detected. The second determining unit47is thus able to detect failures of both the drive unit encoder24and the driven unit encoder27, though it takes time until the failures are detected. The second determining unit47does not output a second cutoff signal if the absolute value of the difference between the first operation quantity Ca and the second operation quantity Cb is equal to or smaller than the third threshold value R3. The principle of a failure determination by the first determining unit46will be described hereinafter with reference toFIGS. 7 through 9.

FIG. 7depicts changes in the values in case the drive unit22is operating normally, as described hereinbefore. Attention is drawn to the absolute value |ΔCa|, indicated by “∘” inFIG. 7, of the first difference ΔCa and the absolute value |ΔCb|, indicated by “x” inFIG. 7, of the second difference ΔCb. While the drive unit22is operating normally, |ΔCa|takes a positive value as Ca increases and remains essentially the same value if the drive unit22is operating at a constant speed. Similarly, |ΔCb| takes a positive value as Cb increases. A value which is approximately one-half of Ca at the time the drive unit22is operating at an expected speed is set as the first threshold value R1. In case the drive unit22is operating normally, if |ΔCa| is smaller than R1, the electric motor23is de-energized. The second threshold value R2is similarly set for ΔCb|. In this example, R2=R1. However, if the drive unit encoder24and the driven unit encoder27have different resolutions and rotational speeds, then it is desirable to determine R1and R2under respective conditions. If |ΔCb| is smaller than R1, then either the electric motor23is de-energized or the electric motor23is energized but the driven unit encoder27is not yet rotated due to the backlash. Conversely, if |ΔCb| is larger than R1, then the electric motor23is rotating. The fact that |ΔCa| is smaller than R1at the time the drive unit22is supplied with electric power indicates that some failure has occurred. If |ΔCb| is larger than R1at this time, then since it indicates that the electric motor23is rotated, the drive unit encoder24that is associated with |ΔCa| is found as failing.

FIG. 8depicts changes in the values in case the drive unit encoder24fails at the time the drive unit22starts operating. Since the drive unit encoder24fails and outputs no pulses in this case, the (i) first operation quantity Ca that is calculated based on the output of the drive unit encoder24and (ii) |ΔCa|remain zero (0). On the other hand, the second operation quantity Cb that is calculated based on the output of the driven unit encoder27starts increasing at a time that lags behind the time at which the electric motor23starts to operate due to the backlash in the same manner as if the drive unit encoder24operates normally. Then, the second operation quantity Cb increases in interlocked relation to the operation of the electric motor23. |ΔCb| exceeds R1at T1when the second operation quantity Cb starts to increase.

In this case, |ΔCa| and |ΔCb| are related to the threshold values as indicated by the following equations (1) and (2):
|ΔCa|<R1  (Equation 1)
|ΔCb|>R2(=R1)  (Equation 2)

When the relationships indicated by the above equations (1) and (2) are satisfied, the first determining unit46operates as described above to determine a failure and the first determining unit46outputs a first cutoff signal. The determination in this case makes it possible to detect a failure at time T1after it has occurred, earlier than T2with respect to the second determining unit47as described above, and hence can stop malfunction due to the failure, more quickly.

FIG. 9depicts changes in the values in case the drive unit encoder24fails at time T5(>T0) while the drive unit22is operating. In this case, since the drive unit22operates in the same way as when it operates normally up to T5, |ΔC| takes a value equal to or larger than R1, and |ΔCb| is 0 up to T0, not depicted, and takes a value equal to or larger than R1after T0. Then, if the drive unit encoder24stops producing pulses at T5, Ca stops increasing, and at next time T6, |ΔCa| becomes 0 and Cb continues to increase, so that |ΔCb| continues to take a value in excess of R1. As the criterion for a failure determination by the first determining unit46is met at this time, the drive unit encoder24is determined as failing. The determination in this case makes it possible to detect a failure at time T6-T5from the occurrence of the failure, earlier than T7-T5with respect to the second determining unit47as described above, and hence can stop malfunction due to the failure, more quickly. The first determining unit46does not output a first cutoff signal if the absolute value of the first difference ΔCa is equal to or larger than the first threshold value R1or if the absolute value of the second difference ΔCb is equal to or smaller than the second threshold value R2. Based on the above operating principles in combination, the manipulator system1according to the present embodiment operates so as to cause a system shutdown in the event of a failure of the drive unit encoder24and the driven unit encoder27, as follows. If the drive unit encoder24fails and stops outputting pulses, then since the absolute value of the first difference ΔCa is smaller than the first threshold value R1and the absolute value of the second difference ΔCb exceeds the second threshold value R2, the criterion for a failure determination by the first determining unit46is met, and the first determining unit46outputs a first cutoff signal. |Ca−Cb| increases, and at the time |Ca−Cb| exceeds R3, the second determining unit47outputs a second cutoff signal to the cutoff unit33. Since the determination by the first determining unit46is earlier than the determination by the second determining unit47, the first cutoff signal is output to the cutoff unit33before |Ca−Cb| exceeds R3, de-energizing the electric motor23that serves as a power source. If the driven unit encoder27fails and stops outputting pulses, then since the absolute value of the first difference ΔCa is larger than the first threshold value R1and the absolute value of the second difference ΔCb does not exceed the second threshold value R2, the criterion for a failure determination by the first determining unit46is not met, and the first determining unit46does not output a first cutoff signal. |Ca−Cb| increases, and at the time |Ca−Cb| exceeds R3, the second determining unit47outputs a second cutoff signal to the cutoff unit33, de-energizing the electric motor23that serves as a power source.

Specific examples of setting the first threshold value R1, the second threshold value R2, and the third threshold value R3will be described below. According to a specific example inFIG. 3, it is assumed that the resolution of the drive unit encoder24is 4000 pulses/revolution. The resolution of the driven unit encoder27is 3600 pulses/revolution. The speed reduction ratio of the speed reducer mechanism25is 36:1. The speed reduction ratio of the gear28is 1:1. The backlash between the electric motor23and the driven unit encoder27, as converted into an angular displacement of the pulley18, is 2 degrees. The backlash between the electric motor23and the drive unit encoder24is 0 degree. The lowest rotational speed of the pulley18at the time the drive unit22is operating is 3 degrees/second.

When the electric motor23is energized at the lowest rotational speed, the drive unit encoder24and the driven unit encoder27output pulses respectively at the following rates:

In order to normalize them, only the count of the pulses from the driven unit encoder27is multiplied by 40, and the result is used as Cb. When the count is sampled at intervals of 100 milliseconds, or 0.1 second, |ΔCa|=|ΔCb|=120. This is the value of |ΔCa| or |ΔCb| at the time the electric motor23is rotated at the lowest rotational speed. Therefore, threshold values used to determine whether the electric motor23is rotated or not should be smaller than the above value. If the threshold values are 0, then since a speed irregularity or a rotation error may be detected as an error. Therefore, the threshold values are set to a value between 0 and the value at the time the electric motor23is rotated at the lowest rotational speed. For example, the threshold values may be set to one-half of the value at the time the electric motor23is rotated at the lowest rotational speed, i.e.,

In a system containing noises and errors, R1may be set to a slightly low value as it used as an upper limit value reference and R2may be set to a slightly high value as it used as a lower limit value reference, thereby avoiding erroneous determinations due to noises and errors.

It is possible to set R1and R2as follows:

Therefore, the first threshold value R1should preferably be equal to or smaller than the second threshold value R2(R1<R2). As the lowest rotational speed of the pulley18is 3 degrees/second, the resolution for counting Ca and Cb is 400 pulses/degree, and the backlash as a dead zone is 2 degrees, so that the third threshold value R3may be selected as follows:

By giving a margin of approximately 10% to the above value, the third threshold value R3may be set as follows:

The third threshold value R3may include a certain margin for the purpose of preventing erroneous determinations due to noises, etc.

Operation of the manipulator system1according to the present embodiment will be described hereinafter with reference toFIG. 10.FIG. 10is a flowchart depicting an outline of operation of the manipulator system1according to the present embodiment. The manipulator system1is used with the surgical instruments6connected to the drive unit22. The manipulator system1is activated in step S101, and the manipulator control device30is initialized in step S102. The drive unit22is moved to a preset position for initialization. When the manipulator control device30is initialized, the counts of pulse signals in the first position calculator34and the second position calculator40are initialized. In subsequent operation, the initialized counts represent displacement 0, and the counts increase or decrease according to pulse signals output from the drive unit encoder24and the driven unit encoder27. Then, the user operates the operation unit4while viewing an image on the display unit3of the operation input device2. The operation unit4outputs an operation signal in accordance with the movement of the user who operates the operation unit4to the manipulator control device30. The manipulator control device30acquires the operation signal from the operation unit4in step S103. The manipulator control device30determines whether the user has input an instruction to terminate the treatment using the operation input device2or not. If no terminating instruction is input as indicated by “No” in step S104, then the control signal generator31generates a control signal based on the operation signal and a first operation quantity in step S105. In the manipulator control device30, the output unit32outputs a drive signal according to the control signal to the cutoff unit33. The cutoff unit33outputs the drive signal to the electric motor23of the drive unit22in step S106. The electric motor23of the drive unit22is now energized according to the operation on the operation unit4. In response to the drive signal from the cutoff unit33, the electric motor23of the drive unit22rotates the output shaft26. At this time, both the drive unit encoder24connected to the electric motor23and the driven unit encoder27indirectly connected to the electric motor23through the output shaft26generate respective pulse signals based on the operation quantity of the electric motor23.

The first position calculator34calculates an operation quantity of the electric motor23based on the pulse signal generated by the drive unit encoder24. The second position calculator40calculates an operation quantity of the electric motor23based on the pulse signal generated by the driven unit encoder27. The operation quantity or a first operation quantity Ca, calculated by the first position calculator34is read into the control signal generator31and used for feedback control as information representing the present displacement of the drive unit22. A second operation quantity Cb calculated by the second position calculator40may be read into the control signal generator31and used for feedback control or the like as information representing the present displacement of the drive unit22. For feedback control in the control signal generator31, either one of the first operation quantity Ca and the second operation quantity Cb may be available for use. Concurrent with its control process for actuating the drive unit22, the manipulator control device30performs a monitoring step in step S200for a failure determination for the drive unit encoder24and the driven unit encoder27. The control process of the manipulator control device30for a failure determination will be described below with reference to a flowchart.FIG. 11is such a flowchart depicting a flow of operation of the failure determination by the first determining unit46and the second determining unit47of the manipulator system1. After the manipulator control device is activated and the surgical instruments6are mounted on the drive unit22, the manipulator control device30initializes the first position calculator34and the second position calculator40in step S201. Since the first position calculator34and the second position calculator40are initialized after the surgical instruments6have been mounted on the drive unit22, the positions and orientations of the surgical instruments6at this time represent their initial positions in the drive unit22. Specifically, when the first position calculator34is initialized, the count of the pulse signal from the drive unit encoder24becomes zero (0). The first operation quantity Ca(n) calculated by the first position calculator34becomes zero (0). When the second position calculator40is initialized, the count of the pulse signal from the driven unit encoder27becomes zero (0) and the second operation quantity Cb(n) calculated by the second position calculator40becomes zero (0). “n” referred to above represents a variable that is reset to zero (0) when the manipulator control device30is initialized.

Then, the manipulator control device30adds 1 to (n) in step S202. After that, the first position calculator34calculates a first operation quantity Ca(n) and the second position calculator40calculates a second operation quantity Cb(n) in step S203. The first operation quantity Ca(n) is output to the first arithmetic logic unit35and the second determining unit47, whereas the second operation quantity Cb(n) is output to the second arithmetic logic unit41and the second determining unit47. Then, the first arithmetic logic unit35of the manipulator control device30substitutes the latest first operation quantity for the first operation quantity Ca(n) corresponding to the variable (n) in step S204. The first arithmetic logic unit35stores the first operation quantity Ca(n) in the position information memory36. In step S204, furthermore, the second arithmetic logic unit41of the manipulator control device30substitutes the latest second operation quantity for the second operation quantity Cb(n) corresponding to the variable (n). The second arithmetic logic unit41stores the second operation quantity Cb(n) in the position information memory42. Then, the first arithmetic logic unit35of the manipulator control device30causes the difference arithmetic logic unit37to calculate a first difference ΔCa in step S205. The first difference ΔCa represents a value calculated by subtracting a first operation quantity Ca(n−1) from the latest first operation quantity Ca(n). The first operation quantity Ca(n−1) is acquired immediately before the latest first operation quantity Ca(n). In step S205, furthermore, the second arithmetic logic unit41of the manipulator control device30causes the difference arithmetic logic unit43to calculate a second difference ΔCb. The second difference ΔCb represents a value calculated by subtracting a second operation quantity Cb(n−1) from the latest second operation quantity Cb(n). The second operation quantity Cb(n−1) is acquired immediately before the latest second operation quantity Cb(n). The first difference ΔCa and the second difference ΔCb are output to the first determining unit46. Then, the manipulator control device30causes the comparative arithmetic logic unit38of the first arithmetic logic unit35to compare the absolute value of the first difference ΔCa and the first threshold value R1with each other, and causes the comparative arithmetic logic unit44of the second arithmetic logic unit41to compare the absolute value of the second difference ΔCb and the second threshold value R2with each other. The results of comparison are output to the first determining unit46.

Then, the first determining unit46combines the (i) result of comparison between the absolute value of the first difference ΔCa and the first threshold value R1and (ii) the result of comparison between the absolute value of the second difference ΔCb and the second threshold value R2, to branch the processing, in step S206. If the absolute value of the first difference ΔCa is smaller than the first threshold value R1and the absolute value of the second difference ΔCb is larger than the second threshold value R2as indicated by “Yes” in step S206, then the first determining unit46outputs a first cutoff signal for deactivating the drive unit22to the cutoff unit33in step S207. If the absolute value of the first difference ΔCa is equal to or larger than the first threshold value R1or the absolute value of the second difference ΔCb is equal to or smaller than the second threshold value R2as indicated by “No” in step S206, then the first determining unit46does not output a first cutoff signal, and control goes to step S208. Then, the manipulator control device30causes the second determining unit47to compare the absolute value of the difference between the first operation quantity Ca and the second operation quantity Cb with the third threshold value R3in step S208. If the absolute value of the difference between the first operation quantity Ca and the second operation quantity Cb is larger than the third threshold value R3as indicated by “Yes” in step S208, then the second determining unit47outputs a second cutoff signal for deactivating the drive unit22to the cutoff unit33in step S209. If the absolute value of the difference between the first operation quantity Ca and the second operation quantity Cb is equal to or smaller than the third threshold value R3as indicated by “No” in step S208, then the second determining unit47does not output a second cutoff signal, and control goes back to step S202. When a first cutoff signal or a second cutoff signal is output to the cutoff unit33, the cutoff unit33, seeFIG. 4, enters the OFF state in which the drive signal is inhibited from being output to the drive unit22. Specifically, the cutoff unit33of the manipulator control device30switches its energizing state to the ON state or the OFF state based on whether it is receiving a first cutoff signal or not, i.e., whether the first determining unit46determines that the absolute value of the first difference ΔCa is smaller than the first threshold value R1and the absolute value of the second difference ΔCb exceeds the second threshold value R2, or not. If the cutoff unit33is receiving a first cutoff signal, then the cutoff unit33switches to the OFF state in which the current output to the drive unit22is cut off. Thus, when the cutoff unit33receives a first cutoff signal, the drive unit22is deactivated. If the cutoff unit33is not receiving a first cutoff signal, then the cutoff unit33switches its energizing state to the ON state or the OFF state based on whether it is receiving a second cutoff signal or not, i.e., whether the absolute value of the difference between the first operation quantity Ca and the second operation quantity Cb is in excess of the third threshold value R3or not. If the cutoff unit33is receiving a second cutoff signal, then the cutoff unit33switches to the OFF state in which the current output to the drive unit22is cut off. Thus, when the cutoff unit33receives a second cutoff signal, the drive unit22is deactivated. When at least either one of first and second cutoff signals is thus output to the cutoff unit33, the drive unit22is not actuated, stopping the surgical instruments6from operating, even if an operation is input to the operation input device2. When the cutoff unit33switches to the OFF state, it may output information indicating that there is a possibility of failure and it has stopped the surgical instruments6from operating, to the display unit3or the like in step S210. Heretofore, it has been known that an encoder connected to an electric motor may be determined as failing if a signal from the encoder remains unchanged continuously for a certain period of time even when the electric motor is energized. According to such a process, the electric motor needs to operate beyond (i) an error allowed on the encoder itself and (ii) an error such as a backlash or the like in the power transfer path until the encoder is determined as failing after it has failed. Therefore, the electric motor is operated for a short period of time despite the failure of the encoder.

According to the present embodiment, in case the drive unit encoder24does not output a pulse signal due to a failure, the first determining unit46is able to detect the failure of the drive unit encoder24earlier than the second determining unit47. As a result, the manipulator system1according to the present embodiment can quickly stop the surgical instruments6from operating in the event that the drive unit encoder24fails and is unable to output a pulse signal. Furthermore, since the second determining unit47is provided in the manipulator control device30, the manipulator system1can stop the surgical instruments6from operating in case the drive unit encoder24outputs an inaccurate pulse signal due to a failure thereof or the driven unit encoder27suffers a failure. The probability that the drive unit encoder24and the driven unit encoder27which have been operating normally will fail at the same time is very low, and the probability that either one of the drive unit encoder24and the driven unit encoder27will fail earlier than the other is high. Consequently, because of the arrangement according to the present embodiment, the manipulator system1is capable of detecting a failure of either one of the drive unit encoder24and the driven unit encoder27. Especially, the manipulator system1is capable of quickly detecting a failure of the drive unit encoder24. Therefore, the manipulator system1can enter a safe state, i.e., a state in which the surgical instruments6are shut off, in the event of a failure of the power transfer to the surgical instruments6.

A second embodiment will be described hereinafter.FIG. 12is a schematic view depicting a drive unit and a driven unit of a manipulator system1A according to the second embodiment.FIG. 13is a block diagram of the manipulator system1A. The manipulator system1A according to the present embodiment is different from the first embodiment described above in that the drive unit22and the driven unit15can be detachably attached by the user, and the manipulator system1A includes a connect/disconnect sensor29for detecting whether the drive unit22and the driven unit are attached to one another. According the present embodiment, the connect/disconnect sensor29is disposed in the drive unit22. The connect/disconnect sensor29is electrically connected to a manipulator control device30A.

The connect/disconnect sensor29has a switch that is turned on when the driven unit15is properly attached to the drive unit22and is turned off when the driven unit15is detached from the drive unit22. A connect/disconnect mechanism for the drive unit22and the driven unit15may include a screw19depicted inFIG. 16that couples a casing of the drive unit22and a casing of the driven unit15to each other, so that drive unit22and the driven unit15can detachably be attached to one another. The connect/disconnect sensor29may have a microswitch29A disposed in the drive unit22. When the driven unit15is attached to the drive unit22by the screw19, the microswitch29A is turned on by being pushed by the casing of the driven unit15. The driven unit has a coupling16engageable with the output shaft26of the drive unit22. The coupling16is connected to a rotational shaft17fixed to the pulley18. The connect/disconnect mechanism for the drive unit22and the driven unit15is not limited to the mechanism described above, but may include hooks22aon the drive unit22for securing the driven unit15to the drive unit22, as depicted inFIG. 17. When the driven unit15is attached to the drive unit22by the hooks22a, the microswitch29A is turned on. The connect/disconnect sensor29is not limited to the switch described above, but may be any sensor insofar as it is capable of detecting whether the drive unit22and the driven unit15are attached to each other. The state of the connect/disconnect sensor29, indicating whether it is turned on or off, is referred to the manipulator control device30A.

The manipulator control device30A includes a mode selector48in addition to the control signal generator31, the output unit32, the cutoff unit33, the first position calculator34, the first arithmetic logic unit35, the second position calculator40, the second arithmetic logic unit41, the first determining unit46, and the second determining unit47according to the first embodiment. The mode selector48selects an operation mode of the manipulator control device30A according to a detected state from the connect/disconnect sensor29. The mode selector48is connected to the connect/disconnect sensor29in order to be able to refer to a detected state from the connect/disconnect sensor29. When the driven unit15is detached from the drive unit22, the mode selector48prohibits the first determining unit46from operating and permits the second determining unit47to operate. When the driven unit15is attached to the drive unit22, the mode selector48permits the first determining unit46and the second determining unit47to operate. According to the present embodiment, since the second determining unit47is always permitted to operate, the mode selector48is connected to the first determining unit46in order to selectively operate the first determining unit46.

Operation of the manipulator system1A according to the present embodiment will be described hereinafter.FIGS. 14 and 15are flowcharts depicting a flow of operation of the manipulator system1A according to the present embodiment when in use. The manipulator system1A is activated, initializing various components thereof in step S301. The manipulator control device30A is self-diagnosed in step S302. If the manipulator control device30A is malfunctioning as indicated by “Yes” in step S303, then an error is displayed in step S304, and the manipulator system1A is shut off in step S305. If the manipulator control device30A is not malfunctioning, then the manipulator system1A enters a mode for waiting for the surgical instruments6to be attached. In the state for waiting for the surgical instruments6to be attached, the drive unit22is self-diagnosed in step S306. If the drive unit22is determined in its self-diagnosis as malfunctioning as indicated by “Yes” in step S307, then an error is displayed in step S304, and the manipulator system1A is shut off in step S305. If the drive unit22is determined in its self-diagnosis as not malfunctioning as indicated by “No” in step S307, then a message is displayed on the display unit3for prompting the user to attach the surgical instruments6to the respective drive units22. The manipulator system1A stands by in the state for waiting for the surgical instruments6to be attached in step S308. Whether each of the surgical instruments6is attached to the corresponding drive unit22or not is determined based on the state of the connect/disconnect sensor29, indicating whether it is turned on or off. If the surgical instruments6are determined as being attached to the respective drive units22as indicated by “Yes” in step S309, then the manipulator control device30A operates in a mode for actuating the surgical instruments6to perform a treatment. If the surgical instruments6are not determined as being attached to the respective drive units22as indicated by “No” in step S309, then the manipulator control device30A stands by in the state for waiting for the surgical instruments6to be attached in step S308. During a period of time from the self-diagnosis of the drive unit22until waiting for the surgical instruments6to be attached, since the driven unit15of each of the surgical instruments6is not attached to the drive unit22, it is not necessary to quickly shut off the surgical instrument6due to a failure of the drive unit22. During the period of time from the self-diagnosis of the drive unit22until waiting for the surgical instruments6to be attached, therefore, the manipulator control device30A performs a monitoring process for a failure determination using only the second determining unit47in step S400.

After the driven unit15of each of the surgical instruments6has been attached to the drive unit22, when the user enters a terminating instruction and the terminating instruction is not the instruction for terminating the treatment, it becomes possible for the user to apply an operation input using the operation input device2. When the user operates the operation input device2, the operation input device2outputs an operation signal to the control signal generator31. The control signal generator31acquires the operation signal output from the operation input device2in step S310. The control signal generator31determines whether a treatment is to be performed using the surgical instruments6or not based on whether a terminating instruction is input or not. If no terminating instruction is input and the user has indicated its intention to terminate the treatment as indicated by “Yes” in step S311, then the control signal generator31(i) discards the acquired operation signal, (ii) controls the display unit3or the like to display an operation termination of the manipulator5in step S312, and (iii) shuts down the manipulator system1A in step S313. After the manipulator system1A has been shut down, it can be operated again by a predetermined operation such as entering a terminating instruction. If a terminating instruction is input and the treatment is not to be terminated as indicated by “No” in step S311, the control signal generator31generates a control signal depending on an operation signal, and outputs the control signal to the output unit32in step S314. The output unit32outputs a drive signal for actuating the drive unit22according to the control signal to the drive unit22via the cutoff unit33in step S316. When the drive signal is output to the drive unit22and the electric motor23of the drive unit22is energized, the drive unit encoder24and the driven unit encoder27that are mechanically coupled to the electric motor23are actuated by drive power generated by the electric motor23. The drive unit encoder24and the driven unit encoder27now generate respective pulse signals. As with the first embodiment, a first operation quantity Ca is acquired for feedback control in step S316, and control goes back to step S310. After the driven unit15of each of the surgical instruments6is attached to the drive unit22, the manipulator system1A is in a state in which the drive unit22can actuate the surgical instrument6to perform a treatment. In this state, the manipulator control device30A performs a monitoring process for a failure determination using the first determining unit46and the second determining unit47, see step S200in the first embodiment.

After the driven unit15of each of the surgical instruments6is attached to the drive unit22, it is repeatedly determined whether the surgical instrument6is properly attached to the drive unit22or not in step S317. After the driven unit15of each of the surgical instruments6is attached to the drive unit22, if the surgical instrument6is detached from the drive unit22or inappropriately attached to the drive unit22, it is determined that the surgical instrument6is not appropriately attached to the drive unit22as indicated by “No” in step S317. Control goes back to step S306, for example and the manipulator system1A enters the mode for waiting for the surgical instruments6to be attached in step S308. In the monitoring process for a failure determination using only the second determining unit47in step S400depicted inFIG. 14, a first operation quantity Ca and a second operation quantity Cb are calculated in step S401, as depicted inFIG. 15. The second determining unit47determines whether the absolute value of the difference between the first operation quantity Ca and the second operation quantity Cb is larger than the third threshold value R3or not in step S402. If the absolute value of the difference between the first operation quantity Ca and the second operation quantity Cb is larger than the third threshold value R3as indicated by “Yes” in step S402, then the second determining unit47outputs a second cutoff signal to the cutoff unit33in step S403. An error message is displayed on the display unit3or the like in step S404, and the manipulator system1A is shut down in step S313.

According to the present embodiment, as described hereinbefore, when the driven unit15is not attached to the drive unit22, a failure of the drive unit encoder24and the driven unit encoder27is detected using the second determining unit47, and when the driven unit15is attached to the drive unit22, a failure of the drive unit encoder24is further detected using the first determining unit46. The state in which the driven unit is attached to the drive unit22means the state in which a treatment is performed using the surgical instrument6. In the event of a failure of each of the encoders, it is preferable to stop the surgical instrument6from operating more quickly than when the driven unit15is not attached to the drive unit22. According to the present embodiment, when the driven unit15is attached to the drive unit22, the connect/disconnect sensor29enables the mode selector48to permit the first determining unit46to operate. Consequently, in the state in which a treatment is performed using the surgical instrument6, the manipulator system1A can quickly enter a safe state, i.e., a state in which the surgical instruments6are shut off, in the event of a failure of the drive unit encoder24.

A third embodiment is now described hereinafter.FIG. 18is a block diagram of a manipulator system1B according to the third embodiment. The manipulator system1B according to the present embodiment is different from the second embodiment described above in that rather than the connect/disconnect sensor29for detecting whether the drive unit22and the driven unit15are attached to one another or are detached from one another, a mode changing switch55is disposed on the operation input device2. The mode changing switch55is electrically connected to a mode selector48of a manipulator control device30B. The mode changing switch55may be of a known structure that can be operated by the user who uses the operation input device2, such as a mechanical switch, a touch panel, or a GUI interface displayed on the display unit3. The mode changing switch55is operated according to the instruction of the user who operates the manipulator system1B to switch between (i) a mode in which both the first determining unit46and the second determining unit47are used and (ii) a mode in which the first determining unit46is not used and only the second determining unit47is used. Since the second determining unit47is always permitted to operate, the mode selector48is connected to the first determining unit46in order to selectively operate the first determining unit46. The manipulator control device30B may be arranged to display on the display unit3a message or the like for prompting the user to enter the mode in which both the first determining unit46and the second determining unit47are used, before a treatment using the surgical instruments6begins. Furthermore, the manipulator control device30B may be arranged to inhibit itself from outputting the drive signal to the drive unit22until the manipulator system1B enters the mode in which both the first determining unit46and the second determining unit47are used.

A fourth embodiment is now described hereinafter.FIG. 19is a block diagram of a manipulator system1C according to the fourth embodiment. The present embodiment is different from the previously described embodiments in that the manipulator system1C performs a failure detection using both the first determining unit46and the second determining unit47when the manipulator system1C operates using the treatment units8of the surgical instruments6, and performs a failure detection using the second determining unit47while shutting off the first determining unit46when the manipulator system1C does not use the treatment units8. Each of the treatment units8of the surgical instruments6according to the present embodiment has a high-frequency knife9A for incising a tissue with electric power supplied from a high-frequency power supply60. The high-frequency knife9A is not limited to any particular structure. The surgical instruments6according to the present embodiment may be of the monopolar type or the bipolar type.

The operation input device2includes a foot switch61for selectively turning on the high-frequency power supply60to supply electric power and turning off the high-frequency power supply60to stop supplying electric power. The foot switch61is electrically connected to the high-frequency power supply60and a manipulator control device30C. The manipulator control device30C has a mode selector48that is electrically connected to the foot switch61. The mode selector48is connected to the foot switch61in order to be able to refer to whether an input is applied to the foot switch61or not. If there is no input applied to the foot switch61, then the mode selector48inhibits the first determining unit46from operating and permits the second determining unit47to operate. If there is an input applied to the foot switch61, then the mode selector48permits the first determining unit46and the second determining unit47to operate.

Operation of the manipulator system1C according to the present embodiment will be described below.FIG. 20is a flowchart depicting a flow of operation of the manipulator system1C according to the present embodiment when in use.

In the operation of the manipulator system1C according to the present embodiment, a control process for the first determining unit46to output a first cutoff signal and a control process for the second determining unit47to output a second cutoff signal are carried out parallel to each other.

The control process for the first determining unit46to output a first cutoff signal is described hereinafter. As with the first embodiment, the first operation quantity Ca(n), the second operation quantity Cb(n), and the variable n are reset in step S501. Therefore, the initial value Ca(0) of the first operation quantity Ca based on the pulse signal from the drive unit encoder24becomes 0, and the initial value Cb(0) of the second operation quantity Cb based on the pulse signal from the driven unit encoder27becomes 0. Then, as with the first embodiment, based on the pulse signals output from the drive unit encoder24and the driven unit encoder27depending on the drive quantity of the drive unit22, the first position calculator34calculates a first operation quantity Ca and the second position calculator40calculates a second operation quantity Cb in step S502. Then, the mode selector48branches the processing according to whether an input is applied to the foot switch61or not in step S503. If no input is applied to the foot switch61as indicated by “No” in step S503, then the mode selector48substitutes the latest first operation quantity Ca and second operation quantity Cb for the latest first operation quantity Ca(n) and second operation quantity Cb(n), respectively in step S504, after which control goes back to step S502. If an input is applied to the foot switch61, then control goes to step S505in which 1 is added to the variable n, after which control goes to step S506. In step S506, the first arithmetic logic unit35of the manipulator control device30C substitutes the latest first operation quantity for the first operation quantity Ca(n) corresponding to the variable n. The first arithmetic logic unit35stores the first operation quantity Ca(n) in the position information memory36. Furthermore, the second arithmetic logic unit41of the manipulator control device30C substitutes the latest second operation quantity for the second operation quantity Cb(n) corresponding to the variable n. The second arithmetic logic unit41stores the second operation quantity Cb(n) in the position information memory42.

Then, the manipulator control device30C causes the difference arithmetic logic unit37of the first arithmetic logic unit35to calculate a first difference ΔCa in step S507. The first difference ΔCa represents a value calculated by subtracting a first operation quantity Ca(n−1) from the latest first operation quantity Ca(n). The first operation quantity Ca(n−1) is acquired immediately before the latest first operation quantity Ca(n). In step S507, furthermore, the manipulator control device30C causes the difference arithmetic logic unit43of the second arithmetic logic unit41to calculate a second difference ΔCb. The second difference ΔCb represents a value calculated by subtracting a second operation quantity Cb(n−1) from the latest second operation quantity Cb(n). The second operation quantity Cb(n−1) is acquired immediately before the latest second operation quantity Cb(n). The first difference ΔCa and the second difference ΔCb are output to the first determining unit46. Then, the manipulator control device30C causes the first determining unit46to branch the processing based on (i) the result of comparison between the absolute value of the first difference ΔCa and the first threshold value R1and (ii) the result of comparison between the absolute value of the second difference ΔCb and the second threshold value R2in step S508. If the absolute value of the first difference ΔCa is smaller than the first threshold value R1and the absolute value of the second difference ΔCb is larger than the second threshold value R2, then the first determining unit46outputs a first cutoff signal for deactivating the drive unit22to the cutoff unit33in step S509. If the absolute value of the first difference ΔCa is equal to or larger than the first threshold value R1or the absolute value of the second difference ΔCb is equal to or smaller than the second threshold value R2, then the first determining unit46does not output a first cutoff signal, and control goes back to step S502.

The control process for the second determining unit47to output a second cutoff signal is now described hereinafter. The second determining unit47calculates a latest first operation quantity Ca and a latest second operation quantity Cb by referring to the first position calculator34and the second position calculator40in step S510. Moreover, the second determining unit47compares the absolute value of the difference between the first operation quantity Ca and the second operation quantity Cb with the third threshold value R3in step S511. If the absolute value of the difference between the first operation quantity Ca and the second operation quantity Cb is larger than the third threshold value R3as indicated by “Yes” in step S511, then the second determining unit47outputs a second cutoff signal to the cutoff unit33in step S512. If the absolute value of the difference between the first operation quantity Ca and the second operation quantity Cb is equal to or smaller than the third threshold value R3as indicated by “No” in step S511, then the second determining unit47does not output a second cutoff signal to the cutoff unit33, and control goes back to step S510. As described, when at least either one of first and second cutoff signals is thus output to the cutoff unit33, the drive unit22is not actuated, stopping the surgical instruments6from operating, even if an operation is input to the operation input device2. After the surgical instruments6have been stopped from operating by at least either one of first and second cutoff signals output to the cutoff unit33, the manipulator control device30C outputs to the display unit3or the like a message indicating that the manipulator system1C including the surgical instruments6has been shut down due to a failure in step S513. Assume the situation that the user operates the foot switch61to turn on or off the supply of electric power from the high-frequency power supply60. When the user operates the foot switch61to turn on the supply of electric power, the mode selector48of the manipulator control device30C of the present embodiment operates the manipulator control device30C in a mode capable of performing a failure determination using the first determining unit46and the second determining unit47. When the operator turns off the supply of electric power using the foot switch61, the mode selector48operates the manipulator control device30C in a mode capable of performing a failure determination not using the first determining unit46but using the second determining unit47.

The manipulator control device30C according to the present embodiment performs a failure determination using the first determining unit46and a failure determination using the second determining unit47parallel to each other. In the absence of an input to the foot switch61for turning on the supply of electric power from the high-frequency power supply60, a failure determination using the first determining unit46is not performed. In the presence of an input to the foot switch61for turning on the supply of electric power from the high-frequency power supply60, a failure determination using the first determining unit46is performed which is capable of detecting a failure of the drive unit encoder24more quickly than a failure determination using the second determining unit47. While the supply of electric power using the high-frequency power supply60is turned on, the high-frequency knife9A of the treatment unit8is energized with a high-frequency current. Therefore, in the event of a failure of the encoder while the energized high-frequency knife9A is in use, it is preferable to quickly shut off the surgical instrument6including the high-frequency knife9A. According to the present embodiment, since a failure determination using the first determining unit46can be performed while the supply of electric power supplied to the high-frequency knife9A is turned on, the surgical instrument6can shut off particularly quickly in the event of a failure of the drive unit encoder24while the high-frequency knife9A is energized.

A modification of the fourth embodiment is now described.FIG. 21is a block diagram depicting a configuration of the modification of the present embodiment. According to the present modification, rather than the foot switch61connected to the manipulator control device30C, a wire for sending a high-frequency current output from the high-frequency power supply60to the treatment unit8is connected to the manipulator control device30C. The manipulator control device30C has a high-frequency current detector50connected to a wire branched from the wire extending from the high-frequency power supply60to the treatment unit8. The high-frequency current detector50controls the mode selector48depending on the supply of a high-frequency current. According to the present modification, if the supply of a high-frequency current is turned on, then the manipulator control device30C operates in a mode in which a failure determination is performed using both the first determining unit46and the second determining unit47. If the supply of a high-frequency current is turned off, then the manipulator control device30C operates in a mode in which a failure determination is performed not using the first determining unit46and using the second determining unit47. The high-frequency current detector50can directly detect when a high-frequency current is supplied to the treatment unit8. Therefore, even if there is a time difference between an operation of the foot switch61and a switching of the supply of a high-frequency current, it is possible to perform a failure determination using both the first determining unit46and the second determining unit47while a high-frequency current is supplied.

In sum, one aspect of the disclosed technology is directed to a manipulator system comprises a power source configured to generate drive power for operating a surgical instrument. A first sensor is configured to detect a first detected value corresponding to a drive quantity of the power source. A second sensor is configured to detect a second detected value corresponding to a drive quantity of the power source. An arithmetic logic unit is configured to calculate an operation quantity of the power source per unit time as a first operation quantity based on the first detected value and calculate an operation quantity of the power source per unit time as a second operation quantity based on the second detected value. An operation input device operable by a user for entering an input. A control signal generator is configured to receive a signal output from the operation input device and generate a control signal for operating the surgical instrument. An output unit is configured to receive the control signal generated by the control signal generator and generate a drive signal for energizing the power source. A determining unit is configured to output a shutoff signal for de-energizing the power source if the first operation quantity is smaller than a first threshold value and the second operation quantity is larger than a second threshold value. The first threshold value is equal to or smaller than the second threshold value. A cutoff unit is configured to cut off the drive signal output from the output unit to the power source in response to the shutoff signal output for de-energizing the power source from the determining unit.

The determining unit is configured to output the shutoff signal if the absolute value of the difference between the first operation quantity calculated based on the first detected value and the second operation quantity calculated based on the second detected value is larger than a third threshold value. And when the first operation quantity is larger than the first threshold value or the second operation quantity is smaller than the second threshold value. The power source of the manipulator system is detachably attached to the surgical instrument and is capable of transmitting the drive power to the surgical instrument when the power source is attached to the surgical instrument. The power source has a connect/disconnect sensor configured to output a connect signal to the determining unit when the surgical instrument and the power source are attached to one another. The determining unit of the manipulator system is configured to output the shutoff signal when the connect signal is input to the determining unit and when the first operation quantity is smaller than the first threshold value and the second operation quantity is larger than the second threshold value.

The manipulator system further comprises an operation unit configured to operate the surgical instrument and the surgical instrument includes an electrode for treating a tissue. The operation unit includes a switch for selectively turning on and off the supply of an electric current to the electrode. The determining unit is configured to calculate a result of comparison between the absolute value of the difference between the first operation quantity calculated based on the first detected value and the second operation quantity calculated based on the second detected value with a third threshold value. In case the supply of an electric current to the electrode is turned off and is configured to output the shutoff signal based on the result of comparison. The determining unit outputs the shutoff signal if the first operation quantity is smaller than the first threshold value and the second operation quantity is larger than the second threshold value, in case the supply of an electric current to the electrode is turned on.

Another aspect of the disclosed technology is directed to a manipulator system comprises an elongated member having at least one joint. An operation input device operable by a user for entering an input. A drive unit is configured to output drive power for actuating the joint in response to the input from the operation input device. A transmitted member rotatable by the drive power output from the drive unit and transmitted thereto. A first sensor is configured to be attached to the drive unit and detects over time an angular displacement of the drive unit when the drive unit actuates the joint and output a first detected value representing the detected angular displacement. A second sensor is configured to be attached to the transmitted member and detects over time an angular displacement of the transmitted member when the drive unit actuates the joint and output a second detected value representing the detected angular displacement. At least one manipulator control device is configured to calculate a first difference representing a change over time in the angular displacement based on the first detected value and a second difference representing a change over time in the angular displacement based on the second detected value. At least one manipulator control device compares the first difference and a first threshold value with one another and compares the second difference and a second threshold value with one another and then controls the drive unit to de-energize the drive unit if the first difference is smaller than the first threshold value and the second difference is larger than the second threshold value.

Although the embodiments of the technology disclosed herein have been described in detail above with reference to the drawings, specific configurational details are not limited to those embodiments, but may include design changes or the like without departing from the scope of the invention. The components illustrated in the above embodiments and modifications may be arranged in appropriate combinations. The present invention is applicable to a manipulator system including remotely controlled surgical instruments.

While various embodiments of the disclosed technology have been described above, it should be understood that they have been presented by way of example only, and not of limitation. Likewise, the various diagrams may depict an example schematic or other configuration for the disclosed technology, which is done to aid in understanding the features and functionality that can be included in the disclosed technology. The disclosed technology is not restricted to the illustrated example schematic or configurations, but the desired features can be implemented using a variety of alternative illustrations and configurations. Indeed, it will be apparent to one of skill in the art how alternative functional, logical or physical locations and configurations can be implemented to implement the desired features of the technology disclosed herein.