Arm-type assist device

Abstract

To provide an arm-type assist device capable of suppressing the occurrence of unintended movements.SOLUTION: An arm-type assist device has an arm, a load detection device 13, and a calculation unit 17. The arm is controlled by a first actuator 26 and a second actuator 33. The calculation unit 17 has a first memory unit 71, a second memory unit 72, a switch unit 73, and a control unit 74. The first memory unit 71 and the second memory unit 72 each store a balance pressure signal related to the balance pressure. The switch unit 73 is switchable between a first state R1 and a second state R2. In the first state R1, the calculation unit 17 outputs a balance pressure signal from each of the first memory unit 71 and the second memory unit 72. In the second state R2, the calculation unit 17 does not output a balance pressure signal from each of the first memory unit 71 and the second memory unit 72. The control unit 74 switches the switch unit 73 from the first state R1 to the second state R2 according to the detected load V1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an arm-type assist device. [Background technology]

[0002] An arm-type assistive device is used when transporting a load such as a relatively heavy part or baggage. When a worker using the arm-type assistive device holds the load with the arm, a force of a magnitude that balances the load is applied by the assistive device via the arm.

[0003] For example, the arm-type assistive device disclosed in Patent Document 1 has a first arm and a second arm as arm members, and a drive air cylinder and an air cylinder as actuators. The arm-type assistive device has a load detection sensor as a load detection device. When a load is held on the arm-type assistive device, the load of the load is detected by the load detection device. Based on the detected load, the arm-type assistive device calculates a balance pressure to be supplied to the actuators so that each arm member is balanced against the load. The balance pressure is supplied to the actuators from a pneumatic device provided outside the arm-type assistive device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-062943 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, a wire break or the like may occur inside the arm-type assistive device, causing the load detection device to detect an abnormal load. In this case, a balance pressure calculated based on the abnormal load is supplied to the actuator. Therefore, if the load detection device detects an abnormal load, the arm-type assistive device may perform an unintended operation. [Means for solving the problem]

[0006] An arm-type assistive device for solving the above problem is an arm-type assistive device having an arm with an arm member controlled by an actuator, a load detection device that outputs a detected load related to the load of a load carried by the arm, and a calculation unit that calculates a balance pressure of the actuator according to the detected load and outputs a balance pressure signal related to the balance pressure of the actuator, wherein the calculation unit has a memory unit that stores the balance pressure signal before it is output from the calculation unit, a switch unit that is switchable between a first state in which the calculation unit does not output the balance pressure signal stored in the memory unit and a second state in which the calculation unit outputs the balance pressure signal stored in the memory unit, and a control unit that switches the switch unit from the first state to the second state in accordance with the detected load.

[0007] In the arm-type assistive device, the storage unit may store the balance pressure signal processed by a moving average. In the above arm-type assistive device, the control unit may switch the switch unit from the first state to the second state when the detected load is not within a predetermined range, and may switch the switch unit from the second state to the first state when the detected load falls within the predetermined range within a predetermined time after the switch unit is switched from the first state to the second state.

[0008] In the above arm-type assistive device, the arm may have a first arm member and a second arm member as the arm members, and a first actuator and a second actuator as the actuators, the first arm member being controlled by the first actuator, and the second arm member being controlled by the second actuator, and the control unit may switch the switch unit from the first state to the second state, so that the calculation unit outputs the balance pressure signal related to the balance pressure of the second actuator from the memory unit in synchronization with outputting the balance pressure signal related to the balance pressure of the first actuator from the memory unit. [Effects of the Invention]

[0009] According to the present invention, it is possible to prevent unintended actions from occurring. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram schematically showing an arm-type assistive device. [Figure 2] FIG. 2 is a block diagram showing the assist control system. [Figure 3] FIG. 3 is a block diagram showing the calculation unit. [Figure 4] FIG. 4 is a diagram showing a schematic view of the operation of the arm-type assist device. [Figure 5] FIG. 5 is a diagram showing a model of the operation of the arm-type assist device. [Figure 6] FIG. 6(a) is a graph showing the change over time of the detected load, and FIG. 6(b) is a graph showing the change over time of the first balance pressure. [Figure 7] FIG. 7(a) is a graph showing the change over time of the detected load, and FIG. 7(b) is a graph showing the change over time of the first balance pressure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, one embodiment of an arm-type assist device will be described with reference to FIGS. <Overall image of the arm-type assistive device> 1 or 2, the arm-type assistive device 10 has an arm 11, a load detection device 13, a calculation unit 17, and a pressure conversion unit 20. The arm-type assistive device 10 also has an A / D conversion unit 18 and a D / A conversion unit 19. The A / D conversion unit 18 connects the load detection device 13 and the calculation unit 17. The D / A conversion unit 19 connects the calculation unit 17 and the pressure conversion unit 20.

[0012] <Arm> As shown in FIG. 1, the arm 11 has a portion near the base end supported on the base B. The arm 11 has a first arm member 21 and a second arm member 31 as arm members. In other words, the arm 11 has a plurality of arm members. The first arm member 21 constitutes the portion of the arm 11 near the base B. The second arm member 31 constitutes the portion of the arm 11 near the tip end. The arm 11 has a connecting arm 41. The connecting arm 41 connects the first arm member 21 and the second arm member 31.

[0013] <First arm member> The first arm member 21 has a base end support member 22 , a tip end support member 23 , a first frame member 24 , and a connecting member 25 .

[0014] The first frame member 24 connects the base end support member 22 and the tip end support member 23. The connecting member 25 extends parallel to and spaced apart from the first frame member 24. The first arm member 21 has a first actuator 26 as an actuator. The first actuator 26 is built into the first arm member 21. The first actuator 26 swings the first frame member 24 relative to the base end support member 22. The first actuator 26 is an actuator driven by air pressure. The first arm member 21 is controlled by the first actuator 26.

[0015] The base end support member 22 is supported by the base B via a first rotary joint 51. The first rotary joint 51 supports the base end support member 22 so as to be rotatable relative to the base B. The base end support member 22 is rotatable about a first vertical axis L1. A base end portion 24a of the first frame member 24 is connected to the base end support member 22 by a first horizontal axis H1. The base end portion 24a is supported by the first horizontal axis H1 so as to be swingable relative to the base end support member 22.

[0016] The tip end portion 24b of the first frame member 24 is connected to the tip end support member 23 by a second horizontal shaft H2. The tip end support member 23 is supported by the second horizontal shaft H2 so as to be able to swing in the vertical direction relative to the tip end portion 24b. A second rotary joint 52 is provided on the upper end surface of the tip end support member 23.

[0017] The first actuator 26 has an air cylinder 27. The air cylinder 27 has a first cylinder tube 27a, a first piston 27b, and an actuating rod 27c. The first piston 27b is slidably housed inside the first cylinder tube 27a. The actuating rod 27c is connected to the first piston 27b.

[0018] A first piston chamber 27s is defined inside the first cylinder tube 27a by a first piston 27b. A seal member (not shown) is attached to the outer peripheral surface of the first piston 27b. A first end of an actuating rod 27c is connected to the first piston 27b. The first piston 27b moves along the axial direction of the first cylinder tube 27a in accordance with the movement of the actuating rod 27c.

[0019] The first actuator 26 has a link member 28. The link member 28 is swingably connected to the second end of the operating rod 27c. A first end of the link member 28 is swingably supported by the base end support member 22, and a second end of the link member 28 is swingably supported at an angle relative to the operating rod 27c. In addition, the first end of the link member 28 is swingably supported by the third horizontal shaft H3.

[0020] An axis (not shown) of the connecting member 25 extends parallel to an axis (not shown) of the first frame member 24. A first end of the connecting member 25 is supported via a third horizontal shaft H3 so as to be swingable in the vertical direction relative to the base end support member 22. A second end of the connecting member 25 is supported via a fourth horizontal shaft H4 so as to be swingable in the vertical direction relative to the tip end support member 23.

[0021] The arm-type assistive device 10 has a parallelogram link mechanism. The parallelogram link mechanism is composed of a first frame member 24, a base end support member 22, a tip end support member 23, and a connecting member 25. When the first frame member 24 and the connecting member 25 swing vertically relative to the base end support member 22 as the operating rod 27c moves relative to the air cylinder 27, the tip end support member 23 moves parallel to the vertical direction. The first frame member 24 and the connecting member 25 each form a long side of a parallelogram. The base end support member 22 and the tip end support member 23 each form a short side of the parallelogram.

[0022] <Connecting arm> A first end of the connecting arm 41 is supported on the upper end surface of the tip support member 23 via a second rotary joint 52. The connecting arm 41 is supported via the second rotary joint 52 so as to be rotatable about a second vertical axis L2 as a rotation center. The connecting arm 41 has a horizontal arm portion 42 extending horizontally. The first end of the connecting arm 41 is formed by the first end of the horizontal arm portion 42. The second end side of the horizontal arm portion 42 has a vertical portion 43 and a support plate portion 44. The vertical portion 43 extends downward from the horizontal arm portion 42. The support plate portion 44 extends horizontally from the vertical portion 43.

[0023] <Second arm member> The second arm member 31 is supported by a vertical portion 43 and a support plate portion 44. The second arm member 31 has a tubular portion 32. The tubular portion 32 is supported by the support plate portion 44 and is fixed to the outer surface of the vertical portion 43.

[0024] The second arm member 31 has a second actuator 33 as an actuator and a guide rod 34. In other words, the arm 11 has multiple actuators. The second actuator 33 is built into the cylindrical portion 32. The second actuator 33 is driven by air. The second arm member 31 is controlled by the second actuator 33. The second actuator 33 is arranged with the axis of the second cylinder tube 33a extending vertically. A piston 33b is housed inside the second cylinder tube 33a. A sealing member (not shown) is attached to the outer peripheral surface of the piston 33b. Within the second cylinder tube 33a, a second piston chamber 33d is defined below the piston 33b. The sealing member (not shown) prevents air from leaking from the second piston chamber 33d.

[0025] In the second actuator 33, a first end of a piston rod 33c is connected to the piston 33b. The piston rod 33c passes through the lower end of the second cylinder tube 33a and the support plate portion 44. The piston rod 33c protrudes from the lower end of the second arm member 31. The guide rod 34 passes through the support plate portion 44 and protrudes from the lower end of the second arm member 31.

[0026] A third rotary joint 53 is connected to the lower end of the second cylinder tube 33a and the lower end of the guide rod 34. An operating unit 12 is fixed to the lower end surface of the third rotary joint 53. When the worker manually operates the arm-type assistive device 10, the worker operates the operating unit 12 to move the arm 11.

[0027] A holding portion 12a is fixed to the lower end of the operating portion 12. The holding portion 12a holds a load W. The holding portion 12a is configured to be able to adsorb the load W at one end thereof, which is different from the end connected to the operating portion 12. The holding portion 12a adsorbs and holds the load W by pressing the end against the load W.

[0028] <Brake device> A brake device (not shown) is provided to each of the first rotary joint 51, the second rotary joint 52, and the third rotary joint 53. The brake device provided to the first rotary joint 51 is configured to be able to restrict rotation of the base end support member 22 relative to the base B. The brake device provided to the second rotary joint 52 is configured to be able to restrict rotation of the connecting arm 41 relative to the tip support member 23. The brake device provided to the third rotary joint 53 is configured to be able to restrict rotation of the operating unit 12 relative to the second arm member 31.

[0029] <Assistance control system> As shown in Fig. 2, the operation of the arm-type assistive device 10 is controlled by an assistive force control system 100. The assistive force control system 100 controls the pressure supplied to the arm-type assistive device 10 from a pressure supply source A. The assistive force control system 100 includes a load detection device 13, a calculation unit 17, and a pressure conversion unit 20. The assistive force control system 100 further includes an A / D conversion unit 18 and a D / A conversion unit 19. The load detection device 13 is included in the operation unit 12.

[0030] As shown in FIG. 1, the controller 101 is disposed near the arm 11. The controller 101 includes a calculation unit 17. The controller 101 is a part of the assist control system 100 that controls the arm 11 based on the output of the load detection device 13. The controller 101 is connected to the load detection device 13 by wiring. The location where the controller 101 is disposed is not limited to this.

[0031] The controller 101 controls the first actuator 26 and the second actuator 33. The controller 101 is configured to be able to stop the operations of the first actuator 26 and the second actuator 33. The controller 101 is configured to be able to stop the operation of the arm 11 by stopping the operations of the first actuator 26 and the second actuator 33.

[0032] The controller 101 is connected to each brake device (not shown). Each brake device is connected to a pressure supply source A. The controller 101 is configured to be able to control the pressure supplied from the pressure supply source A to each brake device. The pressure supplied to each brake device by the controller 101 is converted by each brake device into a braking force that restricts the rotation of each of the first rotary joint 51, the second rotary joint 52, and the third rotary joint 53. When pressure is being supplied to each brake device by the controller 101, the movement of each of the first arm member 21, the connecting arm 41, and the second arm member 31 is restricted. In other words, the controller 101 is configured to be able to stop the movement of the arm 11 by each brake device.

[0033] 1 and 2, the load detection device 13, the calculation unit 17, the first actuator 26, and the second actuator 33 are connected by wiring and piping inside the arm 11. The load detection device 13 detects the load of the load W held by the arm 11. The load detection device 13 outputs a detection signal related to the detected load V1 to the calculation unit 17 via the A / D conversion unit 18. The load detection device 13 outputs the detected load V1 related to the load of the load W carried by the arm 11.

[0034] The load detection device 13 is set so that the detected weight V1 is not zero even when the load W is not held by the holding unit 12a. In other words, the load detection device 13 outputs a non-zero detected weight V1 to the A / D conversion unit 18 even when the load W is not held. Hereinafter, the detected weight V1 detected when the load W is not held will be referred to as a virtual weight. Hereinafter, the detected weight V1 is a weight that takes into account the virtual weight. The detected weight V1 includes a virtual weight that is not dependent on the weight of the load W. The virtual weight is set in advance in the load detection device 13.

[0035] The A / D conversion unit 18 connects the calculation unit 17 and the load detection device 13. The A / D conversion unit 18 converts the analog signal input from the load detection device 13 into a digital signal and inputs it to the calculation unit 17.

[0036] The calculation unit 17 calculates a balance pressure corresponding to the weight of the arm 11 and the detection load V1 for the first actuator 26. Hereinafter, the weight of the arm 11 will be simply referred to as weight. The balance pressure supplied to the first actuator 26 as a result of the calculation will be referred to as a first balance pressure P1. The first balance pressure P1 is a pressure supplied to the first actuator 26 so that the first arm member 21 balances against a load associated with a portion of the arm 11 that is closer to the tip end than the first arm member 21, including the detection load V1.

[0037] The calculation unit 17 calculates a balance pressure corresponding to the weight and the detection load V1 for the second actuator 33. The balance pressure supplied to the second actuator 33 as a result of the calculation is referred to as a second balance pressure P2. The second balance pressure P2 is a pressure supplied to the second actuator 33 so that the second arm member 31 balances against the load associated with the portion of the arm 11 closer to the tip side than the second arm member 31, including the detection load V1.

[0038] The calculation unit 17 outputs a digital signal related to the first balance pressure P1 as a first balance pressure signal as a balance pressure signal. The calculation unit 17 outputs a digital signal related to the second balance pressure P2 as a second balance pressure signal as a balance pressure signal. In other words, the calculation unit 17 outputs a balance pressure signal related to the balance pressure.

[0039] The calculation unit 17 is connected to a pressure conversion unit 20 via a D / A conversion unit 19. The D / A conversion unit 19 has a first D / A conversion unit D1 and a second D / A conversion unit D2. The first D / A conversion unit D1 and the second D / A conversion unit D2 convert each balanced pressure signal input from the calculation unit 17 from a digital signal to an analog signal.

[0040] The pressure conversion unit 20 has a first electropneumatic regulator 14 and a second electropneumatic regulator 15. A first D / A conversion unit D1 is connected to the first electropneumatic regulator 14. A second D / A conversion unit D2 is connected to the second electropneumatic regulator 15. The first D / A conversion unit D1 outputs the first balanced pressure signal converted into an analog signal to the first electropneumatic regulator 14. The second D / A conversion unit D2 outputs the second balanced pressure signal converted into an analog signal to the second electropneumatic regulator 15.

[0041] The first electropneumatic regulator 14 converts the first balance pressure signal into a first balance pressure P1 and outputs it to the first actuator 26. The second electropneumatic regulator 15 converts the second balance pressure signal into a second balance pressure P2 and outputs it to the second actuator 33. The first electropneumatic regulator 14 outputs the first balance pressure P1 to the first actuator 26 in response to the supply of compressed air from the pressure supply source A. The second electropneumatic regulator 15 outputs the second balance pressure P2 to the second actuator 33 in response to the supply of compressed air from the pressure supply source A.

[0042] The calculation unit 17 will be described in detail. The calculation unit 17 has a first calculation unit C1 and a second calculation unit C2. Each of the first calculation unit C1 and the second calculation unit C2 is a part of the calculation unit 17 to which the detection weight V1 converted into a digital signal by the A / D conversion unit 18 is input.

[0043] The first calculation unit C1 stores a plurality of coefficients. Each coefficient is set in advance in the first calculation unit C1. For example, the plurality of coefficients include the total weight from the second rotary joint 52 to the tip end side and the weight of the first arm member 21. The plurality of coefficients also includes a proportionality constant set to consider the ratio at which the first arm member 21 acts as a load on the arm 11. The first calculation unit C1 calculates the first balance pressure P1 by taking the above-mentioned various coefficients into account in the detected load V1. The first calculation unit C1 outputs the calculated first balance pressure P1 to the first D / A conversion unit D1 as a digital signal.

[0044] The second calculation unit C2 stores a plurality of coefficients. Each coefficient is set in advance in the second calculation unit C2. For example, the plurality of coefficients include the total weight from the third rotary joint 53 to the tip side and the weight of the second arm member 31. The plurality of coefficients also includes a proportionality constant set to consider the proportion at which the second arm member 31 acts as a load on the arm 11. The second calculation unit C2 calculates the second balance pressure P2 by adding the above-mentioned various coefficients to the detected load V1. The second calculation unit C2 outputs the calculated second balance pressure P2 to the second D / A conversion unit D2 as a digital signal.

[0045] When the arm-type assist device 10 is being operated by an operator, the volume of the first piston chamber 27s changes. In addition, in this situation, the volume of the second piston chamber 33d changes. Even if the volume of the first piston chamber 27s changes, the internal pressure of the first piston chamber 27s is adjusted by the first electropneumatic regulator 14 to be a constant value. Even if the volume of the second piston chamber 33d changes, the internal pressure of the second piston chamber 33d is adjusted by the second electropneumatic regulator 15 to be a constant value.

[0046] The detected load V1 can change depending on the operation of the arm-type assistive device 10 by the worker. For example, the detected load V1 changes slightly as the worker raises or lowers the holding part 12a. The calculation unit 17 calculates and outputs the first balance pressure P1 and the second balance pressure P2 according to the detected load V1 and the operation status of the arm-type assistive device 10. In other words, each of the first balance pressure P1 and the second balance pressure P2 changes over time depending on the operation of the arm-type assistive device 10.

[0047] <Stop part> The calculation unit 17 has a first memory unit 71 and a second memory unit 72 as memory units, a switch unit 73, and a control unit 74. The first memory unit 71, the second memory unit 72, the switch unit 73, and the control unit 74 configure a stop unit 70.

[0048] The stopping unit 70 is configured to be able to stop the arm 11 in accordance with the detected load V1. In other words, the arm-type assistive device 10 can be stopped by the stopping unit 70 while in operation.

[0049] <First storage unit and second storage unit> The first storage unit 71 is connected to the first calculation unit C1. The first storage unit 71 can also be connected to the first D / A conversion unit D1. In other words, the first calculation unit C1 can also be connected to the first D / A conversion unit D1 via the first storage unit 71.

[0050] The first storage unit 71 receives the first balanced pressure signal calculated by the first calculation unit C1. The first storage unit 71 stores the received first balanced pressure signal. The first storage unit 71 stores the first balanced pressure signal before it is output from the operation unit 17. The first balanced pressure signal output from the first calculation unit C1 changes over time. Therefore, the first balanced pressure signal input to the first storage unit 71 also changes over time. The first storage unit 71 stores the first balanced pressure signal in a time series. In other words, the first storage unit 71 cumulatively stores the first balanced pressure signal output from the first calculation unit C1.

[0051] The first storage unit 71 constantly calculates and stores a first average balanced pressure signal from the first balanced pressure signal stored as a time series. The first storage unit 71 can output the first average balanced pressure signal. The first average balanced pressure signal is calculated by calculating a moving average of the first balanced pressure signal. In other words, the first storage unit 71 stores the first balanced pressure signal processed by the moving average.

[0052] The moving average of the first balanced pressure signal by the first storage unit 71 will be described in more detail. Each time a first balanced pressure signal is input from the first calculation unit C1, the first storage unit 71 calculates a first average balanced pressure signal. The first storage unit 71 references the first balanced pressure signal input before the input. Specifically, the first storage unit 71 references the first balanced pressure signal stored from one second before the input to the input. The first storage unit 71 calculates a time average of the referenced first balanced pressure signal and stores the result of this calculation as the first average balanced pressure signal. In other words, at the time when the first balanced pressure signal is input, the first storage unit 71 performs averaging using the first balanced pressure signal from a certain time before the input. Note that the time referenced by the first storage unit 71 to perform time averaging is not limited to one second. For example, the first storage unit 71 may reference a first balanced pressure signal from more than one second before the input of the first balanced pressure signal to perform time averaging.

[0053] The second storage unit 72 is connected to the second calculation unit C2. The second storage unit 72 can also be connected to the second D / A conversion unit D2. In other words, the second calculation unit C2 can also be connected to the second D / A conversion unit D2 via the second storage unit 72.

[0054] The second storage unit 72 receives the second balanced pressure signal calculated by the second calculation unit C2. The second storage unit 72 stores the received second balanced pressure signal. The second storage unit 72 stores the second balanced pressure signal before it is output from the operation unit 17. The second balanced pressure signal output from the second calculation unit C2 changes over time. Therefore, the second balanced pressure signal input to the second storage unit 72 also changes over time. The second storage unit 72 stores the second balanced pressure signal in a time series. In other words, the second storage unit 72 cumulatively stores the second balanced pressure signal output from the second calculation unit C2.

[0055] The second storage unit 72 constantly calculates and stores a second average balanced pressure signal from the second balanced pressure signal stored as a time series. The second storage unit 72 can output the second average balanced pressure signal. The second average balanced pressure signal is calculated by taking a moving average of the second balanced pressure signal. In other words, the second storage unit 72 stores the second balanced pressure signal processed by the moving average. The calculation of the second average balanced pressure signal by the second storage unit 72 is performed in the same manner as the calculation of the first average balanced pressure signal by the first storage unit 71. Therefore, a detailed description of the calculation of the second average balanced pressure signal will be omitted.

[0056] <Switch section> The switch unit 73 is connected to each of the first D / A conversion unit D1 and the second D / A conversion unit D2. The switch unit 73 can switch between a first state R1 and a second state R2. The first state R1 is a state in which the first D / A conversion unit D1 and the first calculation unit C1 are connected without the first storage unit 71, and the second D / A conversion unit D2 and the second calculation unit C2 are connected without the second storage unit 72. In the first state R1, the first calculation unit C1 outputs a first balanced pressure signal to the first D / A conversion unit D1. In the first state R1, the second calculation unit C2 outputs a second balanced pressure signal to the second D / A conversion unit D2. In other words, the first state R1 is a state in which the calculation unit 17 does not output the balanced pressure signals stored in the first storage unit 71 and the second storage unit 72.

[0057] The second state R2 is a state in which the first D / A conversion unit D1 and the first calculation unit C1 are connected via the first storage unit 71, and the second D / A conversion unit D2 and the second calculation unit C2 are connected via the second storage unit 72. Therefore, the first D / A conversion unit D1 receives the first average balanced pressure signal from the first storage unit 71 as the first balanced pressure signal. Furthermore, the second D / A conversion unit D2 receives the second average balanced pressure signal from the second storage unit 72 as the second balanced pressure signal. In other words, the second state R2 is a state in which the calculation unit 17 outputs the balanced pressure signals stored in each of the first storage unit 71 and the second storage unit 72.

[0058] <Control unit> The control unit 74 controls the first memory unit 71, the second memory unit 72, and the switch unit 73. The control unit 74 is connected to the A / D conversion unit 18. A digital signal corresponding to the detection weight V1 is input to the control unit 74 from the A / D conversion unit 18. In other words, the detection weight V1 converted by the A / D conversion unit 18 is input to the control unit 74. The control unit 74 switches the switch unit 73 from the first state R1 to the second state R2 in accordance with the detection weight V1. Hereinafter, the detection weight V1 converted by the A / D conversion unit 18 will be referred to as a digitized weight.

[0059] Consider a situation in which the control unit 74 switches the switch unit 73 from the first state R1 to the second state R2. In this case, the calculation unit 17 outputs a first balance pressure signal related to the first balance pressure P1 of the first actuator 26 from the first memory unit 71. In synchronization with the output from the first memory unit 71, the calculation unit 17 outputs a second balance pressure signal related to the second balance pressure P2 of the second actuator 33 from the second memory unit 72.

[0060] The control unit 74 stores a predetermined range. The predetermined range is a range related to the magnitude of the detection load V1. As shown in FIGS. 6(a) and 7(a), the predetermined range is a range in which the detection load V1 is equal to or less than an upper threshold Vmax and equal to or greater than a lower threshold Vmin. The predetermined range is set in the control unit 74 in a state converted into a digital signal. For example, the operator sets the predetermined range in the control unit 74 by setting the lower threshold Vmin and the upper threshold Vmax in advance in the state converted into a digital signal.

[0061] The lower limit threshold Vmin is set to a value smaller than the virtual load set in the load detection device 13. The upper limit threshold Vmax is set to a value larger than the virtual load. In other words, the virtual load is within a predetermined range.

[0062] Each time a digitized weight is input, the control unit 74 compares the magnitude of the detection weight V1 corresponding to the input digitized weight with the lower limit threshold Vmin. At the same time, the control unit 74 compares the magnitude of the detection weight V1 corresponding to the input digitized weight with the upper limit threshold Vmax. In this way, the control unit 74 determines whether the detection weight V1 corresponding to the input digitized weight is within a predetermined range.

[0063] Consider a situation in which the switch unit 73 is in the first state R1. In this situation, the control unit 74 switches the switch unit 73 to the second state R2 when the detection weight V1 corresponding to the input digitized weight becomes smaller than the lower threshold Vmin. Also, in this situation, the control unit 74 switches the switch unit 73 to the second state R2 when the detection weight V1 corresponding to the input digitized weight becomes larger than the upper threshold Vmax. In other words, the control unit 74 switches the switch unit 73 from the first state R1 to the second state R2 when the detection weight V1 is not within a predetermined range.

[0064] When the control unit 74 switches the switch unit 73 from the first state R1 to the second state R2, it stops the first memory unit 71 from storing the first balanced pressure signal. That is, in the second state R2, the first memory unit 71 does not store the first balanced pressure signal input from the first calculation unit C1. While the switch unit 73 is in the second state R2, the first memory unit 71 outputs the first average balanced pressure signal calculated immediately before the switch unit 73 changes from the first state R1 to the second state R2.

[0065] When the control unit 74 switches the switch unit 73 from the first state R1 to the second state R2, it stops the second memory unit 72 from storing the second balanced pressure signal. That is, in the second state R2, the second memory unit 72 does not store the second balanced pressure signal input from the second calculation unit C2. While the switch unit 73 is in the second state R2, the second memory unit 72 outputs the second average balanced pressure signal calculated immediately before the switch unit 73 changes from the first state R1 to the second state R2.

[0066] After switching the switch unit 73 from the first state R1 to the second state R2, if the detected load V1 falls within a predetermined range within a predetermined time, the control unit 74 switches the switch unit 73 from the second state R2 to the first state R1. The predetermined time is a time interval set in advance in the control unit 74. The predetermined time is set based on the time required for the worker to hold the load W on the holding unit 12a. In this embodiment, the predetermined time is 1.5 seconds. However, the predetermined time is not limited to 1.5 seconds.

[0067] If the detected load V1 does not fall within the predetermined range within a predetermined time after the switch unit 73 is switched from the first state R1 to the second state R2, the control unit 74 outputs a signal to that effect to the controller 101. The controller 101 stops the operation of the first actuator 26 and the second actuator 33. In this case, the controller 101 also restricts the rotation of the first rotary joint 51, the second rotary joint 52, and the third rotary joint 53. The first actuator 26, whose operation has been stopped by the controller 101, is supplied with the first balance pressure P1 related to the first average balance pressure signal. The second actuator 33, whose operation has been stopped by the controller 101, is supplied with the second balance pressure P2 related to the second average balance pressure signal.

[0068] <Operation of the arm-type assistive device> The operation of the arm-type assistive device 10 will be described together with the operation of the arm-type assistive device 10 to transport a load W. Consider a situation in which the arm-type assistive device 10 is being operated by a worker (not shown). Before the load W is held on the holding portion 12a of the arm-type assistive device 10, the switch unit 73 is in the first state R1. Before the load W is held on the holding portion 12a, the load detection device 13 outputs a virtual load. In other words, before the load W is held on the holding portion 12a, the detected load V1 is the virtual load.

[0069] First, the operation of the arm-type assist device 10 when transporting a load W to a desired position will be described. 4 and 5 show a state in which the arm-type assistive device 10 is operating while holding a load W. The arm-type assistive device 10 has the load W attached to the holding portion 12a. The load W is attached to the holding portion 12a by pressing the end of the holding portion 12a against the load W. In the state shown in FIG. 4, a first balancing pressure P1 is supplied to the first actuator 26. Also, a second balancing pressure P2 is supplied to the second actuator 33. Therefore, the arm 11 is balanced with respect to the load W. Hereinafter, the state in which the arm 11 is balanced with respect to the load W will be referred to as a balanced state. That is, FIG. 4 shows the arm 11 in a balanced state.

[0070] 5, in response to an operation by a worker (not shown), the arm-type assist device 10 raises a load W. At this time, in order for the arm 11 to be in a balanced state with the load W raised, a first balance pressure P1 and a second balance pressure P2 are supplied to the first actuator 26 and the second actuator 33, respectively.

[0071] The worker transports the load W by moving the operating unit 12 in the vertical or horizontal direction while the load W is being held. When the load W reaches the desired position in the vertical or horizontal direction, the worker places the load W at the desired position. Once the load W is placed at the desired position, the worker stops holding the load W with the holding unit 12a. This causes the load W to separate from the arm-type assistive device 10.

[0072] 7(a) and 7(b) show the changes over time of the detected load V1 and the first balance pressure P1. The second balance pressure P2 is not qualitatively different from the first balance pressure P1. Hereinafter, we will focus on the first balance pressure P1, and will not explain the changes over time of the second balance pressure P2. Accordingly, we will also not explain the second calculation unit C2 and the second storage unit 72.

[0073] When the load W is placed, the location where the weight of the load W acts shifts from the holder 12a to the location where the load W is placed. For example, when the worker places the load W on a table, the location where the load W generates a load shifts from the holder 12a to the table at the time the load W is placed on the table. Furthermore, during the process of placing the load W, the end of the holder 12a is slightly pushed into the location where the load W is placed. At this time, the load detection device 13 detects a negative load. When the magnitude of the negative load matches the magnitude of the virtual load, the detected load V1 becomes zero.

[0074] The point in time when the detected load V1 becomes zero is referred to as the second point in time T2. As the load W is placed in the desired location, the holder 12a stops attracting the load W. The point in time when the holder 12a stops attracting the load W is referred to as the third point in time T3. After the third point in time T3, the detected load V1 increases until it becomes a load corresponding to the virtual load. The detected load V1 is zero between the second point in time T2 and the third point in time T3.

[0075] The detection load V1 decreases as the operator lowers the operating unit 12. For example, the inertia of the holding unit 12a can be cited as a factor that causes the detection load V1 to decrease. The detection load V1 becomes smaller than the lower limit threshold Vmin before the second time point T2. The time point at which the detection load V1 decreases and reaches the lower limit threshold Vmin is referred to as the first time point T1. After the third time point T3, the detection load V1 becomes larger than the lower limit threshold Vmin. For example, the inertia of the holding unit 12a can be cited as a factor that causes the detection load V1 to increase. The time point at which the detection load V1 increases and reaches the lower limit threshold Vmin is referred to as the fourth time point T4. The detection load V1 remains equal to or smaller than the lower limit threshold Vmin between the third time point T3 and the fourth time point T4.

[0076] The point in time 1.5 seconds after the first point in time T1 is referred to as the fifth point in time T5. The fourth point in time T4 is between the first point in time T1 and the fifth point in time T5. The time from the first point in time T1 to the fifth point in time T5 is the predetermined time in this case.

[0077] Hereinafter, the operation of the stopping unit 70 at each point in time will be described with reference to FIGS. 7(a) and 7(b). Before the first time point T1, the switch unit 73 is in the first state R1. At the first time point T1, the detection weight V1 decreases and reaches the lower limit threshold Vmin. In other words, when the switch unit 73 is in the first state R1, the detection weight V1 becomes a value outside the predetermined range. Then, the control unit 74 switches the switch unit 73 from the first state R1 to the second state R2.

[0078] Between the first time point T1 and the fourth time point T4, the switch unit 73 is in the second state R2. At the fourth time point T4, the detection weight V1 increases and reaches the lower threshold value Vmin. In other words, with the switch unit 73 in the second state R2, the detection weight V1 reaches a value within the predetermined range before the fifth time point T5. Therefore, the control unit 74 switches the switch unit 73 from the second state R2 to the first state R1.

[0079] The first balance pressure P1 before the first time point T1 is obtained by converting the first balance pressure signal calculated by the first calculation section C1 using the first D / A conversion section D1. The first balance pressure P1 between the first time point T1 and the fourth time point T4 is obtained by converting the first average balance pressure signal output from the first storage unit 71 by the first D / A converter D1. That is, the first balance pressure P1 is a constant value between the first time point T1 and the fourth time point T4.

[0080] The first balance pressure P1 after the fourth time point T4 is obtained by converting the first balance pressure signal calculated by the first calculation section C1 by the first D / A conversion section D1. Next, referring to Figures 6(a) and 6(b), an operation when an abnormality occurs in the arm-type assist device 10 during the process of transporting the load W will be described. Here, a case will be considered where an abnormality occurs in the arm-type assist device 10, causing a sudden increase in the detected load V1. For example, an abnormality that can cause a sudden increase in the detected load V1 is a disconnection in the wiring connecting the load detection device 13 and the controller 101. The operation of the worker sucking the load W onto the holder 12a has been described above, and therefore a description thereof will be omitted.

[0081] The time when an abnormality occurs in the arm-type assistive device 10 is referred to as the abnormality occurrence time TE. After the abnormality occurrence time TE, the detected load V1 increases rapidly. The time when the detected load V1 reaches the upper limit threshold Vmax due to the rapid increase in the detected load V1 is referred to as the sixth time T6.

[0082] At the sixth point in time T6, the control unit 74 switches the switch unit 73 from the first state R1 to the second state R2. After the sixth point in time T6, the calculation unit 17 outputs the first average balance pressure signal stored in the first storage unit 71. The first electropneumatic regulator 14 supplies the first balance pressure P1 corresponding to the first average balance pressure signal to the first actuator 26. In other words, the first balance pressure P1 after the sixth point in time T6 is a constant value.

[0083] The point 1.5 seconds after the sixth point T6 is referred to as the seventh point T7. In other words, the time from the sixth point T6 to the seventh point T7 is the predetermined time in this case. The detected load V1 at the seventh point T7 is greater than the upper threshold Vmax. In other words, the detected load V1 at the seventh point T7 is not within the predetermined range. Therefore, at the seventh point T7, the controller 101 stops the operation of the arm 11. In the arm 11 whose operation has been stopped, the first actuator 26 is supplied with the first balance pressure P1 that was supplied immediately before the seventh point T7.

[0084] [Effects of this embodiment] The effects of this embodiment will be described. (1) The arm-type assist device 10 can supply the first balance pressure P1 and the second balance pressure P2 corresponding to the detected load V1 to the first actuator 26 and the second actuator 33, respectively, by the calculation unit 17. Even if the detected load V1 is not intended by the worker due to an internal wire break or the like, the arm-type assist device 10 can control the operation of the arm 11 by switching the switch unit 73 with the control unit 74. This allows the arm-type assist device 10 to prevent the arm 11 from jumping up or the like due to an internal wire break or the like.

[0085] Furthermore, by connecting the first actuator 26 to the first memory unit 71 and the second actuator 33 to the second memory unit 72, the arm 11 can maintain a balanced state even after it has stopped. In other words, by having the first memory unit 71 and the second memory unit 72, the arm-type assist device 10 can prevent the stopped arm 11 from falling due to loss of power. As described above, the arm-type assist device 10 can prevent unintended movements from occurring.

[0086] (2) The arm 11 in the second state R2 is controlled by the first average balance pressure signal stored in the first memory unit 71 and the second average balance pressure signal stored in the second memory unit 72. As a result, when the switch unit 73 is switched from the first state R1 to the second state R2, the arm-type assist device 10 can control the arm 11 with a value close to the balance pressure that was supplied to the arm 11 immediately before the switching. For example, compared to when the arm 11 is controlled in the second state R2 with a pressure that is significantly different from the balance pressure that was supplied immediately before the switching, the difference in balance pressure before and after the switching can be made smaller. As a result, the arm-type assist device 10 can prevent abrupt changes in the operation of the arm 11 before and after stopping.

[0087] (3) When the control unit 74 switches the switch unit 73 from the first state R1 to the second state R2, the arm-type assist device 10 can stop the operation of the arm 11 after a predetermined time has elapsed. This allows the arm-type assist device 10 to continue operating without stopping the operation even if the detected load V1 becomes zero during the operation of pressing the load W against the holding unit 12a. Therefore, the arm-type assist device 10 can improve the work efficiency in transporting the load W compared to, for example, a case in which the controller 101 stops the arm 11 at the same time that the switch unit 73 switches to the second state R2.

[0088] (4) The control unit 74 switches the switch unit 73 from the first state R1 to the second state R2, thereby connecting the first memory unit 71 to the first actuator 26 and connecting the second memory unit 72 to the second actuator 33. For example, the arm-type assistive device 10 can stop the arm 11 with a simpler configuration than when the control unit 74 individually controls the connections of the first memory unit 71 and the second memory unit 72. In other words, the arm-type assistive device 10 can suppress unintended movements of the arm 11 without the control unit 74 performing complex control.

[0089] (5) The arm-type assist device 10 sets the predetermined time based on the time required for the worker to hold the load W on the holding portion 12a, thereby preventing the arm 11 from stopping during the process of attracting the load W to the holding portion 12a. This allows the arm-type assist device 10 to improve work efficiency in holding the load W while shortening the time from when an internal abnormality occurs until the arm 11 stops.

[0090] (6) The predetermined time and the predetermined range are set in advance in the arm-type assist device 10. This allows the settings to be changed depending on the environment in which the arm-type assist device 10 is installed, the type of load W to be transported, etc.

[0091] (7) By setting a virtual load in the load detection device 13, the arm-type assist device 10 can set the switch unit 73 to the first state R1 even when the holding portion 12a is not holding a load W.

[0092] [Example of change] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0093] The arm-type assistive device 10 may be configured with three or more arm members as the multiple arm members. In this case, the arm-type assistive device 10 may have an actuator for each of the three or more arm members, and may also have a memory unit that can be connected to each actuator via the switch unit 73. Furthermore, each of the control unit 74 and the switch unit 73 may be configured to be able to individually control the connection between each memory unit and each actuator.

[0094] The arm-type assist device 10 may have one arm member. The predetermined range does not have to be set in the control unit 74. In other words, the control unit 74 does not have to determine whether the detected load is within the predetermined range. For example, the control unit 74 may be configured to be able to receive input from the worker, and may switch the switch unit 73 from the first state R1 to the second state R2 in response to the input from the worker.

[0095] The predetermined time does not have to be set in the control unit 74. For example, the control unit 74 may be configured to be able to receive input from an operator, and may stop the operation of the arm 11 using the controller 101 in response to the input from the operator.

[0096] The first storage unit 71 does not have to store the first balanced pressure signal processed by the moving average. The second storage unit 72 does not have to store the second balanced pressure signal processed by the moving average. In this case, for example, the first storage unit 71 in the second state R2 may output the first balanced pressure signal calculated by the first calculation unit C1 immediately before switching from the first state R1 to the second state R2. The second storage unit 72 in the second state R2 may output the second balanced pressure signal calculated by the second calculation unit C2 immediately before switching from the first state R1 to the second state R2.

[0097] The assisting device to which the controller 101 is connected is not limited to the arm-type assisting device 10 of this embodiment. In short, it may be any assisting device that has a load detecting device 13 and is configured with an actuator that is driven in response to the detection result of the load detecting device 13 and the arm 11.

[0098] The situation in which the controller 101 stops the operation of the arm 11 is not limited to a situation in which the detected load V1 suddenly increases due to an abnormality occurring inside the arm-type assist device 10. For example, the controller 101 can stop the operation of the arm 11 even in a situation in which the detected load V1 suddenly decreases due to an abnormality occurring inside the arm-type assist device 10.

[0099] The calculation unit 17 does not need to have multiple storage units. For example, the calculation unit 17 may have only one storage unit. In this case, the storage unit receives the balanced pressure signals from the first calculation unit C1 and the second calculation unit C2. The storage unit is also connected to the first D / A conversion unit D1 and the second D / A conversion unit D2. The calculation unit 17 is configured to be able to output the balanced pressure signals from the storage unit to the first D / A conversion unit D1 and the second D / A conversion unit D2 using the switch unit 73.

[0100] The control unit 74 may switch the switch unit 73 from the first state R1 to the second state R2 even when the detected load V1 reaches the upper limit threshold Vmax in a situation where no abnormality has occurred inside the arm-type assistive device 10. When the detected load V1 reaches the upper limit threshold Vmax as a result of the operator operating the operation unit 12, the control unit 74 may switch the switch unit 73 from the first state R1 to the second state R2. For example, in FIG. 6, the sixth point in time T6 may be before the abnormality occurrence point in time TE. In this case, the control unit 74 switches the switch unit 73 from the first state R1 to the second state R2 at the sixth point in time T6.

[0101] The control unit 74 may control the first memory unit 71, the second memory unit 72, and the switch unit 73 when the load W is not being held by the arm 11. For example, in the arm-type assist device 10 that is not holding the load W, even when the detected load V1 falls outside the predetermined range due to an internal abnormality or the like, the control unit 74 switches the switch unit 73 from the first state R1 to the second state R2.

[0102] The holding portion 12a does not have to be configured to be able to adsorb the load W. For example, the holding portion 12a may hold the load W by using any of a clamp, a hook, and a fork. In short, it is sufficient that the holding portion 12a is configured to be able to hold the load W.

[0103] [Note] The technical ideas that can be understood from the above-described embodiment and modifications will be described below. (i) The detected load includes a virtual load that is not dependent on the load of the load, and the virtual load is within the predetermined range and is preset in the load detection device. [Explanation of symbols]

[0104] 10...arm-type assist device, 11...arm, 13...load detection device, 17...calculation unit, 21...first arm member, 26...first actuator, 31...second arm member, 33...second actuator, 71...first memory unit as memory unit, 72...second memory unit as memory unit, 73...switch unit, 74...control unit, R1...first state, R2...second state, W...load.

Claims

1. an arm having an arm member, the arm member being controlled by an actuator; a load detection device that outputs a detected load related to the load being transported by the arm; a calculation unit that calculates a balance pressure of the actuator according to the detected load and outputs a balance pressure signal related to the balance pressure of the actuator, The calculation unit a storage unit that stores the balance pressure signal before it is output from the calculation unit; a switch unit that is switchable between a first state in which the calculation unit does not output the balance pressure signal stored in the storage unit and a second state in which the calculation unit outputs the balance pressure signal stored in the storage unit; a control unit that switches the switch unit from the first state to the second state in response to the detected load.

2. The arm-type assist device according to claim 1 , wherein the storage unit stores the balance pressure signal processed by a moving average.

3. 3. The arm-type assist device according to claim 1, wherein the control unit switches the switch unit from the first state to the second state when the detected load is not within a predetermined range, and switches the switch unit from the second state to the first state when the detected load falls within the predetermined range within a predetermined time after the switch unit is switched from the first state to the second state.

4. The arm has a first arm member and a second arm member as the arm member, The actuators include a first actuator and a second actuator, the first arm member is controlled by the first actuator, the second arm member is controlled by the second actuator, 3. The arm-type assist device according to claim 1, wherein the control unit switches the switch unit from the first state to the second state, so that the calculation unit outputs the balance pressure signal related to the balance pressure of the second actuator from the memory unit in synchronization with outputting the balance pressure signal related to the balance pressure of the first actuator from the memory unit.

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