Hoisting machine and hoisting machine system

Abstract

Provided are: a hoisting machine capable of smoothly mounting a member on a mounting surface; a hoisting machine system; and a method for using the hoisting machine system. A hoisting machine 1 comprises: a hoisting means 25; a drive motor 22 for rotating the hoisting means 25; a load calculation means 100b for calculating the load of the hoisting means 25; and a motor control means 100 for controlling the drive motor 22. The motor control means includes: a first torque control mode in which the torque of the drive motor 22 is controlled on the basis of a reference torque Tm0 corresponding to a reference load and a load torque Tl corresponding to the load; and a second torque control mode in which the torque of the drive motor 22 is controlled so that the torque is smaller by a predetermined amount as compared to the first torque control mode.

Description

Hoists and Hoist Systems

[0001] The present invention relates to a hoist and a hoist system.

[0002] The work (lifted object) can be placed on a placement surface by using a hoist and then lowering the hoist. In this operation, it is necessary to avoid damaging the work when placing it on the placement surface, so operating the hoist is complicated and requires skill.

[0003] Japanese Patent Application Publication No. 6-32592

[0004] Patent Document 1 discloses a method of lowering a workpiece by lowering a hoist. The hoist lowers the workpiece near a mounting surface on which the workpiece is placed using speed control that controls the lowering speed, and then stops. The hoist then lowers the workpiece in accordance with the operating force applied by the operator using force control that allows the workpiece to be lowered using only the operator's operating force. This prevents the workpiece from being lowered with a force greater than that applied by the operator.

[0005] However, even if an operator applies an operating force to the workpiece, if the operator does not control the workpiece to the appropriate position and posture, the workpiece may receive a reaction force from the placement surface, which may cancel out the operator's operating force or the workpiece may bounce back, making it difficult to smoothly place the part on the placement surface.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide a hoist and a hoist system that can smoothly place a workpiece on a placement surface.

[0007] A hoist according to one aspect of the present invention is a hoist that raises and lowers a workpiece by winding up or lowering a load chain or rope from the hoist main body, and is equipped with hoisting means that is arranged on the hoist main body, has a load chain or rope wound around it, and winds up or lowers the load chain or rope in response to rotation, a drive motor that generates a driving force to rotate the hoisting means, load calculation means that calculates the load applied to the hoisting means via the load chain or rope that suspends the workpiece, and motor control means that controls the drive motor, and the motor control means has a first torque control mode that controls the torque of the drive motor based on a reference torque corresponding to a predetermined reference load and a load torque corresponding to the load, and a second torque control mode that controls the torque of the drive motor so that the torque is a predetermined amount smaller than in the first torque control mode.

[0008] A hoist system according to one aspect of the present invention is a hoist system comprising: a hoist that raises and lowers a workpiece by winding up or lowering a load chain or rope from a hoist main body; holding means that is connected to the lower end of the load chain or rope and holds the workpiece from above; a robot device that is connected to the holding means and moves the holding means; and a crane that follows the horizontal movement of the holding means so that the hoist is positioned above the holding means, in which the hoist is disposed on the hoist main body, has a load chain or rope wound around it, and is configured to wind up or lower the load chain or rope in response to rotation; and a driving force that generates a driving force to rotate the hoisting means. The hoisting machine includes a drive motor for driving the hoisting means, a load calculation means for calculating the load applied to the hoisting means via the load chain or rope that suspends the holding means, and a motor control means for controlling the torque of the drive motor based on the load, and the motor control means has a first torque control mode for controlling the torque of the drive motor based on a reference torque corresponding to a predetermined reference load and a load torque corresponding to the load, and a second torque control mode for controlling the torque of the drive motor so that the torque is a predetermined amount smaller than that in the first torque control mode, and when working to lower a workpiece suspended by the hoisting machine toward a placement surface on which it will be placed, the second torque control mode is selected by the motor control means.

[0009] A hoist system according to one aspect of the present invention is a hoist system comprising: a hoist that raises and lowers a workpiece by winding up or lowering a load chain or rope from a hoist main body; holding means that is connected to the lower end of the load chain or rope by a connecting member and holds the workpiece from above; a robot device that is connected to the holding means and moves the holding means; and a crane that follows the holding means as it moves horizontally, so that the hoist is positioned above the holding means. The hoist is arranged on the hoist main body, has a load chain or rope wound around it, and includes hoisting means that winds up or lowers the load chain or rope in response to rotation; a drive motor that generates a driving force to rotate the hoisting means; and a load chain that suspends the holding means. The robot includes a load calculation means for calculating the load applied to the hoisting means via the chain or rope, a position calculation means for calculating the payout length of the load chain or rope from the hoisting means, and a motor control means for controlling the drive motor based on the load calculated by the load calculation means, wherein the motor control means has a position control mode for performing position control based on the payout length calculated by the position calculation means, and the holding means includes a connecting member, an engagement mechanism connected to the lower part of the connecting member and for detachably engaging with the workpiece, a robot support member supported by the robot device, a guide member for guiding the robot support member so that it can slide up and down relative to the connecting member and the engagement mechanism, and a fixing mechanism for fixing the robot support member to the guide member.

[0010] According to the present invention, it is possible to provide a hoist and a hoist system that can smoothly place a member on a placement surface.

[0011] FIG. 1 is a configuration diagram showing the overall configuration of a hoist according to this embodiment. FIG. 2 is a configuration diagram showing the control configuration of the hoist according to this embodiment. FIG. 3 is an enlarged configuration diagram showing the control configuration of a hoist control unit. FIG. 4 is a configuration diagram showing the configuration of a cylinder operating device of the hoist shown in FIG. 1. FIG. 5 is a flowchart showing the control flow of the hoist according to this embodiment. FIG. 6 is a schematic diagram showing how fitting assembly members are fitted and assembled by the hoist according to this embodiment. FIG. 7 is a schematic diagram showing the overall configuration of a fitting assembly system according to this embodiment. FIG. 8 is a configuration diagram showing the control configuration of the fitting assembly system according to this embodiment. FIG. 9 is an operation table showing the operation of each component of the fitting assembly system according to this embodiment. FIG. 10 is a schematic diagram showing the state of each component of the fitting assembly system according to this embodiment. FIG. 11 is a schematic diagram showing the state of each component of the fitting assembly system according to this embodiment. FIG. 12 is a schematic diagram showing the state of each component of the fitting assembly system according to this embodiment. FIG. 13 is a schematic diagram showing the state of each component of the fitting assembly system according to this embodiment.

[0012] Hereinafter, the hoist 1 and fitting assembly systems 10, 20 according to this embodiment will be described with reference to the drawings. The fitting assembly system 10 corresponds to a hoist system, and a method of using the fitting assembly system 10 corresponds to a method of using a hoist system.

[0013] [Hoist 1] (Structure) First, the hoist 1 and a fitting method using the hoist 1 will be described with reference to Fig. 1 to Fig. 6. Fig. 1 is a configuration diagram showing the overall configuration of the hoist 1 according to this embodiment. Fig. 2 is a configuration diagram showing the control configuration of the hoist 1 according to this embodiment. As shown in Fig. 1, the hoist 1 includes a hoist main body 2, an upper hook 3, a cylinder operating device 4, and a chain bucket 5 that holds a wound-up load chain C1.

[0014] The hoist main body 2, which serves as the main body of the hoist 1, can be suspended from a predetermined location such as a ceiling via an upper hook 3. The hoist main body 2 has, inside a housing 21, a drive motor 22, a speed reduction mechanism 23, a brake mechanism 24, a load sheave 25 that winds up the load chain C1, a load sensor 26, a hoist control unit 100, and a driver 27. The winding mechanism consisting of the load chain C1 and the load sheave 25 may be a winding mechanism consisting of a wire rope and a winding drum (not shown). In this case, the wound wire rope is held by the winding drum, making the chain bucket 5 unnecessary.

[0015] The drive motor 22 is a motor that provides a driving force to drive the load sheave 25. In this embodiment, the drive motor 22 is a servo motor equipped with a detector (encoder 22a) that can detect the position (the payout length of the load chain C1), and is preferably an AC servo motor. Note that the AC servo motor is preferably a synchronous motor, but the drive motor 22 may also be a combination of an induction motor and an encoder.

[0016] The speed reduction mechanism 23 reduces the speed of the rotation of the drive motor 22 and transmits it to the load sheave 25. The brake mechanism 24 releases the braking force by electromagnetic force when the drive motor 22 is operating, and generates braking force to hold the load P when the drive motor 22 is not operating.

[0017] The load sheave 25, which serves as a hoisting means, rotates to hoist up and down the load chain C1. The load sheave 25 has a plurality of chain pockets along its outer periphery into which the metal rings of the load chain C1 fit.

[0018] The load sensor 26 measures the load applied to the upper hook 3. The load sensor 26 measures and detects the total load of the load on the hoist main body 2, the load on the load chain C1, and the load P. The load calculation unit 100b of the hoist control unit 100 can calculate the load applied to the load sheave 25 via the load chain C1 by subtracting the main body weight, etc. from the total load measured and detected using the load sensor 26. The load sensor 26 is attached, for example, to a mounting shaft for attaching the upper hook 3 to the hoist main body 2. In this embodiment, the load sensor 26 is a load cell equipped with a strain gauge. However, in addition to the above load cell, a crane scale or the like may be used as long as it has the accuracy and responsiveness sufficient for torque control.

[0019] In addition to the above, the load sensor 26 may be placed anywhere that can detect and measure the load applied to the load sheave 25 by the load chain C1 that suspends the load P, such as between the upper hook 3 and the crane trolley, between the lower hook 6 and the load P, or between the end of the load chain C1 and the lower hook 6.

[0020] The hoist control unit 100 calculates the load torque applied to the load sheave 25 from the load detected by the load sensor 26, and gives command values ​​such as control mode, position, speed, torque, etc. to the driver 27.

[0021] The driver 27 adjusts the externally supplied power to an appropriate power based on the current value of the drive motor 22, the output of the encoder 22a, a command value for motor drive control given from the hoist control unit 100, etc., and gives the power to the drive motor 22 to rotate the drive motor 22. In this embodiment, since the drive motor 22 is a servo motor, the driver 27 is a servo driver. Therefore, the driver 27 has at least a speed control mode and a torque control mode, and selectively executes the speed control mode or the torque control mode based on a command from the hoist control unit 100. The drive motor 22 may be a combination of an induction motor, an encoder, and a vector control type inverter control device, or any other motor capable of torque control and position or speed control.

[0022] The cylinder operating device 4 is an operating device that can be operated by an operator while being held by hand. The cylinder operating device 4 is connected to the lower end side of the load chain C1, and a lower hook 6 for hanging a load P is connected to the cylinder operating device 4.

[0023] An example of a control block for a float mode, which is a torque control mode executed by the hoist control unit 100 and will be described later, will now be described with reference to the enlarged view of Fig. 3. The hoist control unit 100 is a computer that includes, for example, a CPU (Central Processing Unit), memory 100a (RAM (Random Access Memory), ROM (Read Only Memory), internal storage, external storage device, etc.), and an input / output interface. The memory 100a stores control programs for operating in a switch operation mode, which will be described later, and in float modes including a normal float mode and a fitting assembly float mode.

[0024] The hoist control unit 100 also has a load calculation unit 100b as load calculation means, a position calculation unit 100c as position calculation means, and a PI control unit 100d. The load calculation unit 100b calculates the load torque applied to the load sheave 25 via the load chain C1 based on the load detected by the load sensor 26. The position calculation unit 100c calculates the payout length of the load chain C1 from the load sheave 25 based on a position signal output by the driver 27. The PI control unit 100d performs PI (proportional integral) control of the increase / decrease motor torque Th, which is the deviation between the reference torque stored in the memory 100a and the load torque calculated by the load calculation unit 100b.

[0025] The hoisting machine control unit 100 adds the load torque output from the load calculation unit 100b to the value calculated by the PI control unit 100d and transmits the result as a new torque command value to the driver 27. As a result, the hoisting machine control unit 100 performs feedback control so that the deviation between the reference torque and the load torque becomes zero. Note that other control methods using the reference torque, load torque, increased / decreased motor torque, and torque command will be described later.

[0026] 4 is a diagram showing the configuration of the cylinder operating device 4. As shown in FIG. 4, the cylinder operating device 4 includes an operation mode changeover switch 41, a movable grip 42, and a displacement sensor 43.

[0027] In addition, the cylinder operating device 4 is not limited to an operating device connected to the lower hook 6, but may be an operating device (pendant switch) suspended by a cable from the main body of the hoist 1, or may be a wireless remote control device in which the operating unit and the hoist main body 2 are not connected by a wire.

[0028] The operation mode selector switch 41 is a switch for switching the operation mode of the drive motor 22, and a switch signal of the operation mode selector switch 41 is output to the hoist control unit 100. There are two operation modes: a switch operation mode and a float mode, which is a torque control mode, and the float mode includes a first torque control mode and a second torque control mode. In the embodiment, the first torque control mode is referred to as a normal float mode, and the second torque control mode is referred to as a fitting assembly float mode. The differences between the first torque control mode (normal float mode) and the second torque control mode (fitting assembly float mode) will be described later. The switch operation modes include a position control mode and a speed control mode.

[0029] When an operator presses the operation mode changeover switch 41, the hoist control unit 100 switches the operation mode of the drive motor 22 between a switch operation mode and a float mode. In the switch operation mode, the hoist control unit 100 outputs a speed control command to the driver 27 to control the speed of the drive motor 22 based on a signal from a displacement sensor 43 serving as a speed command input device, and in the float mode, the hoist control unit 100 outputs a torque control command to control the torque of the drive motor 22 based on load information from the load sensor 26.

[0030] The movable grip 42 is a grip that is operated when the operation mode of the drive motor 22 is switched to the switch operation mode. The movable grip 42 is provided so as to be slidable in the vertical direction and is held in a neutral position by a biasing member such as a spring. The operator can slide the movable grip 42 upward or downward from the neutral position against the biasing force of the biasing member. The displacement sensor 43 outputs a detection signal corresponding to the amount of sliding of the movable grip 42 to the hoist control unit 100. The hoist control unit 100 controls the speed of the drive motor 22 based on the detection signal.

[0031] The chain bucket 5 stores and holds the unloaded load chain C1 that has already been wound up and is located on the opposite side of the load sheave 25 from the lower hook 6.

[0032] (Control) Next, the control of the hoist 1 will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the control flow of the hoist 1 according to this embodiment. The control flow is executed by the hoist control unit 100.

[0033] In step S1, the hoist control unit 100 determines whether or not an ON signal has been input from the operation mode selector switch 41 of the cylinder operating device 4. If it is determined that an ON signal has been input from the operation mode selector switch 41 (Yes), the process proceeds to step S7. If it is determined that an ON signal has not been input from the operation mode selector switch 41 (No), the process proceeds to step S2.

[0034] In step S2, the hoist control unit 100 determines whether the movable grip 42 is sliding upward. If it is determined that the movable grip 42 is sliding upward (Yes), the process proceeds to step S3. If it is not determined that the movable grip 42 is sliding upward (No), the process proceeds to step S4.

[0035] In step S3, the hoisting machine control unit 100 outputs a hoisting speed command to the driver 27 so that the hoisting speed of the load sheave 25 increases in proportion to the amount the operator slides the movable grip 42 upward, and returns the processing to step S2.

[0036] In step S4, the hoist control unit 100 determines whether the movable grip 42 is sliding downward. If it is determined that the movable grip 42 is sliding downward (Yes), the process proceeds to step S5. If it is not determined that the movable grip 42 is sliding downward (No), the process proceeds to step S6.

[0037] In step S5, the hoist control unit 100 outputs a winding-down speed command to the driver 27 so that the winding-down speed of the load sheave 25 increases in proportion to the amount the operator slides the movable grip 42 downward, and returns the processing to step S4.

[0038] In step S6, the hoist control unit 100 outputs a stop command to the driver 27 to stop the rotation of the drive motor 22.

[0039] In step S1, if an ON signal is input from the operation mode selector switch 41 (Yes), the hoist control unit 100 determines that a float mode command has been input, and the process proceeds to step S7. In step S7, the hoist control unit 100 determines whether or not the operator has pressed and held the operation mode selector switch 41 for one second or more (ON signal input). If it is determined that the operation mode selector switch 41 has been pressed and held for one second or more (Yes), the process proceeds to step S9, and if it is not determined that the operation mode selector switch 41 has been pressed and held for one second or more (No), the process proceeds to S8.

[0040] The hoist control unit 100 sets the time for determining whether the processing of this step should proceed to step S8 or step S9 to 1 second, but it may be set to a time shorter or longer than 1 second as long as it does not complicate the worker's operations.

[0041] Hereinafter, the case where the process proceeds to step S8 will be referred to as the "normal float mode" (first torque control mode), and the case where the process proceeds to step S9 will be referred to as the "fitting assembly float mode" (second torque control mode). The normal float mode is a mode in which the load P is maintained in a suspended state unless a vertical external force is applied to the load P, and the fitting assembly float mode is a mode in which the load P slowly descends even if a vertical external force is not applied to the load P. In both float modes, the load P can be moved vertically by applying an external force to the load P in the hanging direction. Hereinafter, unless otherwise specified, the mere notation "float mode" is a general term that combines the "normal float mode" (first torque control mode) and the "fitting assembly float mode" (second torque control mode).

[0042] In the following description, the torque command value Tm is calculated using the "set load WlO" and the "measured load Wl." However, the "set load WlO" corresponds to the "reference load," and the "measured load Wl" corresponds to the "load." The "reference torque TmO" is calculated from the "set load WlO," and the "load torque Tl" is calculated from the "measured load Wl." Therefore, the torque command value Tm in the "float mode" may be calculated using only the torque value by using the "reference torque TmO" instead of the "set load WlO" and the "load torque Tl (Nm)" instead of the "measured load Wl." In other words, the "set load WlO" and the "reference torque TmO" correspond to the "reference load," and the "measured load Wl" and the "load torque Tl (Nm)" correspond to the "load." The "load" varies in real time based on the output value of the load sensor 26.

[0043] In step S8, which is executed in the normal float mode, the hoist control unit 100 sets the set load W10 based on the following (Equation 1), and proceeds to step S10.

[0044] Set load Wl0 = Measured load Wl (Equation 1) The measured load Wl (N) is the load obtained by subtracting the weight of the main body and the like from the load value measured by the load sensor 26, and is the load that attempts to rotate the load sheave 25 in the winding down direction, and is calculated by the load calculation unit 100b in the hoisting machine control unit 100. The set load Wl0 (N) is the measured load Wl calculated at the start of the float mode and stored in memory 100a, and is a reference load used in control of the float mode.

[0045] Although the set load W10 has been described as being calculated each time the float mode is started, if the load of the load P is known in advance, this load can be stored in memory 100a in advance and used as the reference load during the float mode, so that calculation is not required each time. Also, it is possible to use a combination of storing the load in memory 100a and calculating the set load each time.

[0046] In step S9, which is executed in the fitting assembly float mode, the hoist control unit 100 sets the set load W10 (N) based on the following (Equation 2), and proceeds to step S10.

[0047] Set load Wl0=Measurement load Wl-Pressure load Pa (Equation 2) The pressure load Pa (N) is a load value that is set in advance and stored in the memory 100a. The pressure load Pa (N) will be described later.

[0048] In step S10, the hoist control unit 100 calculates the torque command value Tm (Nm) using the following (Equation 3), (Equation 4), and (Equation 5) based on the set load Wl0 (N) set in step S8 or step S9 and the operating force Ws (N) described later.

[0049] Tm0 = (1 / i) x r x Wl0 (Equation 3) Th = (1 / i) x r x Ws (Equation 4) Tm = Tm0 + Kl x Th (Equation 5) where i is the reduction ratio of the reduction mechanism 23, r is the operating radius of the load sheave 25, and Kl is the gain.

[0050] That is, the hoist control unit 100 calculates the reference torque Tm0 (Nm), which is the torque of the drive motor 22 corresponding to the set load Wl0 (N), using (Equation 3).

[0051] Next, the increase / decrease motor torque Th (Nm) corresponding to the operating force Ws (N) of the operator is calculated using (Equation 4). The operating force Ws (N) is calculated using the following (Equation 6).

[0052] Ws = WlO - Wl (Equation 6) Note that, although the example shown is one in which the increased / decreased motor torque Th (Nm) is determined from the operating force Ws (N), it may also be determined from the load torque Tl (Nm) corresponding to the measured load Wl (N). The measured load Wl (N) calculated based on the load information output by the load sensor 26 can be converted into the load torque Tl (Nm) applied to the load sheave 25 using the following (Equation 7).

[0053] Tl = (1 / i) x r x Wl (Equation 7) In other words, the hoist control unit 100 calculates the increase / decrease motor torque Th from the difference between the reference torque Tm0 (Nm) stored in the memory 100a and the load torque Tl (Nm) corresponding to the load Wl measured and calculated in real time by the load sensor 26.

[0054] Then, the torque command value Tm (Nm) to be output to the drive motor 22 is calculated using (Equation 5), and is sent to the driver 27, after which the process proceeds to step S11.

[0055] Therefore, in float mode, the controller 21 calculates a reference torque Tm0 (Nm) corresponding to the set load Wl0 (N) set at the start of float mode, and an increased / decreased motor torque Th (Nm) corresponding to the operating force Ws (N) calculated from the difference between the set load Wl0 (N) and the measured load Wl (N) that changes due to an external force. Alternatively, in float mode, the controller 21 sets the torque corresponding to the measured load Wl (N) measured at the start of float mode as the reference torque Tm0 (Nm), and calculates the increased / decreased motor torque Th (Nm) from the difference between the reference torque Tm0 and the load torque Tl corresponding to the measured load Wl (N) that changes due to an external force. The controller 21 then outputs the torque command value Tm calculated using Equation 5 to the driver 27. That is, in the float mode, torque control is performed by calculating the torque command value Tm based on the set load Wl0 (N) or the reference torque Tm0 (Nm) corresponding to the set load Wl0 (N) and the load torque Tl (Nm) calculated in real time from the changing measured load Wl (N).

[0056] As described above, the hoist control unit 100 performs feedforward control of the torque command value Tm and outputs it to the driver 27, but it can also perform this using a feedback control method. Specifically, as shown in Fig. 3, the hoist control unit 100 performs feedback control so that the deviation between the reference torque Tm0 (Nm) and the load torque Tl (Nm) becomes zero.

[0057] In step S11, the hoist control unit 100 determines whether or not to continue the float mode. If the hoist control unit 100 detects an ON signal from the operation mode selector switch 41 of the cylinder operating device 4 or a slide of the movable grip, it ends the float mode and returns to step S2 to execute the switch operation mode. If there is no signal from the cylinder operating device 4, it determines that the float mode should be continued, and returns to step S10 to continue the float mode.

[0058] Here, the fitting assembly float mode will be described in detail.

[0059] The difference between the fitting assembly float mode and the normal float mode is whether or not the set load WlO (N) set when starting either float mode subtracts the pressing load Pa (N) from the measured load Wl (N) at that time, as shown in (Equation 1) and (Equation 2). The pressing load Pa (N) is set to, for example, about 10% of the measured load Wl (N) and not more than 20 (N), but can be changed outside the above range as appropriate depending on the weight of the load P and the assembly work.

[0060] In the normal float mode, the load P is held in a suspended state without handling. In the fitting assembly float mode, the set load W10 (N) is reduced by the pressing load Pa (N) relative to the measured load W1 (N) at the time of setting. Therefore, according to Equation 5, the torque equivalent to (1 + K1) times the pressing load Pa (N) is insufficient when the load P is not handled, causing the load P to descend gently. At this time, when a reaction force equal to 1 times Pa acts on the load P, the descent of the load P stops. In reality, due to the mechanical efficiency of the hoist 1, the descent of the load P stops when the reaction force is less than Pa (N). This simplifies the assembly of the fitting components, prevents excessive force from being applied to the fitting, and allows the assembly position and posture to be easily adjusted to the appropriate range with minimal operating force. Furthermore, when the position and posture enter the appropriate range during adjustment of the assembly position and posture, the load P automatically resumes its descent, allowing the fitting assembly work to proceed.

[0061] Furthermore, in the above step S9, the hoist control unit 100 sets the set load W10 (N) based on (Equation 2), but instead, it may be set based on the following (Equation 2').

[0062] Set load Wl0 = measured load Wl × (1 - assembly pressure coefficient) (Equation 2') where 0 < (assembly pressure coefficient) < 1 Furthermore, as described above, the normal float mode and the fitting assembly float mode may be controlled separately in step S8 and step S9, but the set load Wl0 may be calculated based on (Equation 1) in either step. In this case, the operating force Ws (N) may be calculated based on the following (Equation 6'), and the calculated operating force Ws (N) may be calculated based on the above (Equation 4) and (Equation 5), thereby calculating the torque command value to be output in step S10.

[0063] Ws = Wl0 - (Wl + Pa) (Equation 6') In either case, the set load Wl0 (N) can be relatively reduced, the apparent operating force Ws (N) can be increased, or both can be done to set each value so that the output torque of the drive motor 22 output in the fitting assembly float mode is smaller than the output torque output in the normal float mode.

[0064] Although the control method in the float mode has been described above as a feedforward control method, a feedback control method is also possible. Specifically, the hoist control unit 100 may perform feedback control so that the deviation between the reference torque Tm0 (Nm) reduced by a predetermined amount and the load torque Tl (Nm) becomes zero, or may perform feedback control so that the deviation between the reference torque Tm0 (Nm) and the load torque Tl (Nm) increased by a predetermined amount becomes zero, or may perform feedback control so that the deviation between the reference torque Tm0 (Nm) reduced by a predetermined amount and the load torque Tl (Nm) increased by a predetermined amount becomes zero.

[0065] To summarize the above control, when an operator wishes to operate in the switch operation mode, the operator raises or lowers the load P using the movable grip 42 of the cylinder operating device 4. In other words, when the operator is not operating the movable grip 42, the load P remains suspended and stationary. When the operator slides the movable grip 42 upward, the load P rises at a speed proportional to the amount of sliding. Conversely, when the operator slides the movable grip 42 downward, the load P descends at a speed proportional to the amount of sliding.

[0066] In this way, in the switch operation mode, the worker operates the movable grip 42 to change the vertical position of the load P.

[0067] In contrast, when the operator presses the operation mode selector switch 41 of the cylinder operating device 4 for less than one second to switch to the normal float mode, the set load WlO is set to the measured load Wl (N) calculated based on the load measured by the load sensor 26 at that time. Torque control of the drive motor 22 is performed based on the set set load WlO (N) and the measured load Wl measured and calculated by the load sensor 26, so that the load P is maintained in a suspended state unless an external force is applied to the load P. Note that torque control in the float mode may be performed by storing a reference torque TmO (Nm) corresponding to the set load WlO (N), determining the increase / decrease motor torque Th from the difference between the set load WlO (N), and outputting a torque command value Tm to the driver 27.

[0068] When a vertically upward external force (operating force Ws) is applied to the load P, the measured load Wl decreases accordingly, and the increase / decrease motor torque Th (Nm) calculated using (Equation 6) and (Equation 4) increases, so the torque command value Tm (Nm) calculated using (Equation 5) increases. As a result, the torque of the drive motor 22 increases, and the load P rises to assist the worker. When a downward external force (operating force Ws) is applied to the load P, the measured load Wl increases accordingly, and the increase / decrease motor torque Th (Nm) calculated using (Equation 6) and (Equation 4) decreases, so the torque command value Tm (Nm) calculated using (Equation 5) decreases. As a result, the torque of the drive motor 22 decreases, and the load P descends to assist the worker.

[0069] This makes the load P behave as if it were floating in the air, so the worker can freely raise and lower the load P by simply applying force in the desired direction without having to hold the heavy load.

[0070] On the other hand, when the operator presses the operation mode changeover switch 41 of the cylinder operating device 4 for one second or more to switch to the fitting assembly float mode, the set load W10 (N) is set to a value obtained by subtracting a predetermined pressing load Pa (N) from the measured load W1 (N) calculated based on the load measured by the load sensor 26 at that time. In other words, the torque of the drive motor 22 is always insufficient, so the load P gradually descends even without applying an external force to the load P.

[0071] As a result, when fitting and assembling the fitting assembly members, even if the upper fitting member 121 as a member is lowered and comes into contact with the lower fitting member 131 as a lower member, fitting and assembling can be performed without applying pressure greater than a predetermined level to the lower fitting member 131, and it is also possible to easily adjust the position and posture of the fitting assembly members for fitting and assembling (FIG. 6).

[0072] (Operation) Next, the operation of the hoist 1 will be described with reference to Fig. 6. Fig. 6 is a schematic diagram showing how the hoist 1 according to this embodiment engages the engaging members.

[0073] In Figure 6, an operator uses a hoist 1 to engage an upper engaging member 121, which is a member suspended from a lower hook 6, with a lower engaging member 131, which is a member placed on the floor.

[0074] The upper fitting member 121 is cylindrical and includes two hooks 122 provided at the top and a flange 123 that protrudes horizontally from the vertical plane. The two hooks 122 are fixed to the lower hook 6 of the hoist 1 via a sling chain C2, and the upper fitting member 121 rises and falls in accordance with the rise and fall of the lower hook 6. The flanges 123 each have a bolt hole 123a that passes through in the vertical direction.

[0075] The lower fitting member 131 has a cylindrical shape with a bottom and is placed on the floor with its opening facing upward. The lower fitting member 131 has a mounting surface 131s at the top of the cylindrical portion on which the underside of the flange portion 123 of the upper fitting member 121 is placed. The mounting surface 131s has a plurality of bolt holes 131a formed therein and is positioned so that bolts 124 can be inserted into the upper fitting member 121 and the lower fitting member 131 when they are fitted together.

[0076] The outer diameter of the upper fitting member 121 and the inner diameter of the lower fitting member 131 are set to be approximately the same so that they can slide together when fitted together.

[0077] 6A , the operator switches the operation mode selector switch of the cylinder operating device 4 to normal float mode by pressing it for less than one second. The operator lowers the upper fitting member 121 by, for example, pressing the cylinder operating device 4 or the upper fitting member 121 downward, and stops the upper fitting member 121 at a position slightly above the upper end of the lower fitting member 131. The operator then presses the operation mode selector switch of the cylinder operating device 4 for one second or more to switch to fitting assembly float mode. As a result, the hoisting machine control unit 100 sets the set load Wl0 to the value obtained by subtracting the pressing load Pa from the measured load Wl of the upper fitting member 121, so the torque command value of the drive motor 22 becomes smaller than the value necessary to hold the upper fitting member 121, and the upper fitting member 121 gradually descends at a low speed.

[0078] 6B, when the upper fitting member 121 comes into contact with the lower fitting member 131 and stops moving downward, the worker rotates and rocks the upper fitting member 121 while aligning it. When this operation brings the upper fitting member 121 into a position and posture where it can be fitted, it simultaneously resumes moving downward naturally, and the fitting and assembly process progresses.

[0079] At this time, in the normal float mode, which is not the fitting assembly float mode, the upper fitting member 121 will not descend unless a downward external force is intentionally applied to it. Also, even if a downward external force is applied when the upper fitting member 121 is not in a position and posture that allows it to fit with the lower fitting member 131, that is, when the conditions for fitting are not met, the upper fitting member 121 will not descend due to the reaction force, and adjustment of this is difficult. This situation also occurs when the fitting assembly parts are lowered at an extremely slow speed by controlling the speed of the hoist 1, for example.

[0080] In the fitting assembly float mode, the position and posture of the upper fitting member 121 suspended by the hoist 1 becomes a position and posture that allows fitting, and at the same time, the stopped descent automatically resumes, so that fitting assembly work can be easily performed without requiring skill.

[0081] In FIG. 6C, the operator continues to insert the upper fitting member 121 into the lower fitting member 131, and when the lower surface of the flange portion 123 of the upper fitting member 121 comes into close contact with the upper end surface of the lower fitting member 131, the fitting is completed.

[0082] 6D , an operator aligns the bolt holes 123a in the flange portion 123 of the upper fitting member 121 with the bolt holes 131a in the upper end of the cylindrical portion of the lower fitting member 131. This alignment is performed while the flange portion 123 of the upper fitting member 121 is in contact with the lower fitting member 131, but even if the upper fitting member 121 is heavy, most of its weight is supported by the hoist 1, making it easy to align the bolt holes. The operator passes bolts 124 through the aligned bolt holes 123a, 131a to fasten the upper fitting member 121 and the lower fitting member 131 together. This completes the series of fitting and assembling operations.

[0083] Although FIG. 6 illustrates a fitting assembly operation, the fitting assembly float mode is also effective when assembling a heavy object without a fitting portion. Heavy objects tend to sway and become unstable when floating, making fine adjustments difficult. However, the fitting assembly float mode allows for alignment while the object is placed on the assembly surface using a predetermined pressing force (pressing load Pa) preset for each assembly component, facilitating assembly work. This mode is also effective not only for assembly work, but also for slowly placing a load P without impacting the placement surface. Therefore, it is also effective when stacking loads P on the top surface (placement surface) of an already placed load P, such as a placement platform. Therefore, the fitting assembly float mode is not limited to fitting assembly work, but can also be referred to as a placement float mode (second torque control mode) because it is a float mode that can apply a pressing load Pa to a workpiece, such as a load P, suspended by the hoist 1, on a placement surface on which the same type of workpiece is attached or placed. When an upward external force exceeding the pressure load Pa is applied to the workpiece, the workpiece can be raised, so that it is easy to readjust the positioning relative to the mounting surface.

[0084] [Fitting and Assembly System 10] (Structure) Next, the fitting and assembly system 10 and a method for using the fitting and assembly system 10 will be described with reference to Fig. 7 to Fig. 13. Fig. 7 is a schematic diagram showing the overall configuration of the fitting and assembly system 10 according to this embodiment. Fig. 8 is a configuration diagram showing the control configuration of the fitting and assembly system 10 according to this embodiment.

[0085] The fitting assembly system 10 as an assembly system includes a crane 7 , a hoisting machine 1 , a robot device 8 , and a lifting device 9 .

[0086] The crane 7 has traveling rails 71 and lateral travel rails 72. The traveling rails 71 are two rail members suspended from a ceiling or the like. The lateral travel rails 72 are rail members suspended near both ends of the two traveling rails 71 via trolleys, and are movable along the longitudinal direction of the traveling rails 71.

[0087] 1 and 2, and can be raised and lowered with a hoisting device 9 (described later) suspended therefrom. Furthermore, the lateral travel rails 72 are movable along the traveling rails 71, and the hoisting device 1 is also movable along the lateral travel rails 72, so that the hoisting device 1 can move freely in the horizontal direction. Therefore, even if the hoisting device 9 (described later) moves horizontally by the robot device 8, the hoisting device 1 can follow the movement and always be positioned above the hoisting device 9.

[0088] The robot device 8 has a leg 81, a first joint 82, a second joint 83, a first arm 84, a second arm 85, and a wrist 86. The leg 81 has a first motor 81 a, the first joint 82 has a second motor 82 a, the second joint 83 has a third motor 83 a, and the wrist 86 has a fourth motor 86 a.

[0089] The leg 81 stands upright from an installation surface such as a floor and rotatably supports the first joint 82. The leg 81 houses a first motor therein, and when driven by the first motor, the first joint 82 in contact with the leg 81 can be rotated about an axis perpendicular to the installation surface (hereinafter referred to as the "V axis").

[0090] The first joint 82 is provided on the upper end side of the leg 81, and the first arm 84 is rotatably attached to the first joint 82. The first joint 82 has a second motor. The second motor rotates the first arm 84 around an axis parallel to the installation surface (hereinafter referred to as the "H axis"). Therefore, the first arm 84 can rotate around the V axis by the leg 81, and can also rotate around the H axis by the first joint 82.

[0091] The second joint 83 is rotatably attached to the tip end of the first arm 84, and the second arm 85 is rotatably attached to it. The second joint 83 has a third motor. The third motor rotates the second arm 85 around the H-axis. Therefore, the second arm 85 can rotate around the V-axis by the leg 81, and can also rotate around the H-axis using the second joint 83 as the center.

[0092] The wrist 86 is rotatably attached to the tip of the second arm 85. The wrist 86 has a fourth motor. The fourth motor rotates the wrist 86 about the H-axis and always maintains the wrist 86 at the same angle so that it extends horizontally. The wrist 86 has a hand 86h, which detachably holds a tool, a lifting tool, a workpiece Wa, etc. using magnetic force or an air actuator (not shown).

[0093] The sling device 9 serving as a holding means has a clamping member 91 serving as an engaging mechanism and a hanging member 92 serving as a connecting member.

[0094] The clamping member 91 is formed in a U-shape that opens downward, and accommodates and clamps the workpiece Wa by covering it from above. The clamping member 91 has a chuck mechanism 91a inside a portion that extends vertically. When the clamping member 91 accommodates the workpiece Wa from above, the chuck mechanism 91a protrudes from both sides by an actuator 70a (not shown) and comes into close contact with the workpiece Wa, clamping the sides of the workpiece Wa.

[0095] The hanging member 92 has a base member 92a, a top member 92b, a support 92c, a slide guide 92d, a robot connecting member 92e as a guide member, and a locking mechanism 92f as a fixing mechanism.

[0096] The base member 92a is a plate-like member fixed to the upper surface of the clamping member 91. The top member 92b is a plate-like member suspended from the load chain C1 via the lower hook 6 of the hoist 1, and has an engaging portion for engaging with the lower hook 6. The top member 92b and the base member 92a are connected to each other by a support post 92c provided in the center in the left-right direction of the page in Figure 7 so that a constant distance is maintained between them.

[0097] Two slide guides 92d are provided on both sides of the support column 92c, parallel to the support column 92c, and connected between the top member 92b and the base member 92a. The base member 92a and the top member 92b are integrated by the two slide guides 92d and the support column 92c. The robot linking member 92e, located between the top member 92b and the base member 92a, has insertion holes (not shown) through which the support column 92c is inserted and on both sides of the support column 92c, through which the slide guides 92d are inserted. Guide members (not shown) that slidably guide the robot linking member 92e along the slide guides 92d are fixed to the insertion holes of the robot linking member 92e through which the slide guides 92d are inserted.

[0098] The robot linking member 92e has a locking mechanism 92f that prevents the support column 92c from passing through the insertion hole. The locking mechanism 92f is equipped with an air actuator (not shown) and is capable of a locking operation to grip the support column 92c and an unlocking operation to release the grip. As a result, when the locking mechanism 92f is unlocked, the robot linking member 92e can slide along the slide guide 92d, but when the locking mechanism 92f is in a locking operation, the robot linking member 92e is fixed to the lifting device via the support column 92c and the slide guide 92d.

[0099] Furthermore, one horizontal end of the robot connecting member 92e has a holding portion 92g as a robot support member to which the hand portion 86h of the wrist portion 86 of the robot device 8 is detachably and closely held. Therefore, the robot connecting member 92e is held horizontally by the hand portion 86h of the robot device 8. A so-called tool changer is attached to the holding portion 92g and the hand portion 86h, and the two can be attached and detached automatically or manually.

[0100] When the locking mechanism 92f is performing a locking operation with the hand unit 86h of the robot device 8 closely holding the holding unit 92g, the hand unit 86h and the lifting device 9 are integrally connected via the robot connecting member 92e. When the locking mechanism 92f is performing an unlocking operation, the robot connecting member 92e is slidable along the slide guide 92d between the top member 92b and the base member 92a.

[0101] Note that the hoisting machine 1 controls the hoisting machine 1 so that it supports the weight of the hoisting device 9 and the workpiece Wa, and therefore the robotic device 8 does not support the load of the hoisting device 9 and the workpiece Wa. The robotic device 8 can transport the workpiece Wa together with the hoisting device 9 in three dimensions with little force by moving the hand portion 86h in three dimensions, just as an operator grips the cylinder operating device of the hoisting machine 1 in float mode and transports the load with light force in the desired direction.

[0102] (Control) Next, the control configuration of the fitting and assembling system 10 will be described with reference to Fig. 8. Fig. 8 is a configuration diagram showing the control configuration of the fitting and assembling system 10 according to this embodiment.

[0103] The fitting and assembly system 10 includes, as control units, a main control unit 110, a hoist control unit 100 as a motor control means, a robot control unit 80, a lock control unit 60, and a chuck control unit 70, and includes, as an input unit, an operator switch 51.

[0104] The main control unit 110, the hoist control unit 100, the robot control unit 80, the lock control unit 60, and the chuck control unit 70 are, for example, computers or integrated circuits including a CPU (Central Processing Unit), memory 100a (RAM (Random Access Memory), ROM (Read Only Memory), internal storage, external storage device, etc.), an input / output interface, etc. The operator switch 51 is a switch that is provided on an assembly work panel arranged near the fitting assembling system 10 and is operated by an operator.

[0105] The operator switches 51 include a transport operation switch 51a, a direct teach mode switch 51b, and a completion switch 51c. The operator operates the transport operation switch 51a when intending to start a series of operations of the fitting and assembling system 10, from steps S21 to S30, which will be described below. The direct teach mode switch 51b is a switch that the operator operates when setting the system to a direct teach mode, which will be described later. The completion switch 51c is a switch that the operator operates when the operator determines that a series of fitting and assembling operations has been completed.

[0106] The main control unit 110 performs overall control of the fitting and assembling system 10. The main control unit 110 transmits signals related to control commands to the hoist control unit 100, the robot control unit 80, the lock control unit 60, and the chuck control unit 70.

[0107] As described above, the hoisting machine control unit 100 sends torque commands and speed / position commands to the driver 27 to operate the drive motor 22 based on information such as commands sent from the main control unit 110, signals indicating the status of the robot control unit 80, and the measured load sent from the load sensor 26, thereby hoisting up and lowering the lifting device 9 suspended from the hoisting machine 1.

[0108] Based on the control signal sent from the main control unit 110, the robot control unit 80 sends a control signal to the drivers 80a to 80d of each part having the motors 81a to 83a, 86a so that the motors 81a to 83a, 86a can be controlled in a coordinated manner so that the robot device 8 moves as desired.

[0109] The lock control unit 60 transmits a control signal regarding the fastening or unlocking of a locking mechanism 92f provided on the robot connecting member 92e of the hanging member 92, and activates the actuator 60a provided on the locking mechanism 92f to operate the locking mechanism 92f.

[0110] The chuck control unit 70 transmits a control signal to the chuck mechanism unit 91a of the clamping member 91 as to whether or not to chuck the workpiece Wa, and operates the actuator 70a to switch the chuck mechanism unit 91a.

[0111] The operator switch 51 is operated by the operator to send a control signal to the main control unit 110 indicating that the fitting operation has been completed or that the operation mode of the robot device 8 has been set to the direct teach mode. The force sensor 86s used in the direct teach mode is provided on the wrist 86 of the robot device 8 or on the robot connecting member 92e (see FIG. 7) together with the direct teach lever.

[0112] (Operation) Next, the operation of the fitting and assembling system 10 according to this embodiment will be described with reference to Figures 9 to 13. Figure 9 is an operation table showing the operation of each component of the fitting and assembling system 10 according to this embodiment. This operation table shows, from left to right, the operating state of the fitting and assembling system 10, the operating mode of the hoisting machine 1, the operating state of the robot device 8, the lock state of the locking mechanism 92f of the hanging member 92, the fastening state of the chuck mechanism portion 91a of the clamping member 91, and the switch operation state of the worker. Figure 9 also lists these states in chronological order from top to bottom, showing steps switching at changing timings.

[0113] 7, the fitting and assembling system 10 is on standby with the hoist 1 holding the hoisting device 9 in a suspended state and the robot device 8 not applying any force to the hoisting device 9. At this time, the hoisting machine control unit 100 is in the position control mode, and the lock control unit 60 is on standby with the lock mechanism of the hoisting member in the released state. At this time, the robot connecting member 92e is located between the base member 92a and the top member 92b and closer to the top member 92b than the intermediate position between them, but is not in contact with the top member 92b.

[0114] In step S21, the fitting and assembling system 10 moves the lifting device 9 to the picking position for the workpiece Wa in response to the operator's operation of the transport operation switch 51a. First, the hoist 1 transitions to normal float mode and stores the set load W10 (N). Next, the lock control unit 60 sends a fastening command signal for the actuator 60a. The main control unit 110 receives a fastening completion command from the actuator 60a and starts automatic operation of the robot device 8, controlling the operation of the leg 81, first joint 82, second joint 83, first arm 84, second arm 85, and wrist 86. During this time, the lock mechanism 92f of the hanging member 92 remains fastened, and the chuck mechanism 91a of the clamping member 91 remains released. As a result, the hoist 1 and the robot device 8 cooperate to move the lifting device 9 to the position where the workpiece Wa is chucked.

[0115] In step S22, the main control unit 110 receives information from the robot control unit 80 that the lifting device 9 has reached the position for chucking the workpiece Wa, and causes the lock control unit 60 to release the lock mechanism 92f. At this time, the hoist control unit 100 transitions to position control.

[0116] It should be noted that the position control of the hoist 1 can be replaced with the speed control described in the switch operation mode in the hoist 1 used in the fitting and assembly work described above. In the above case, the worker slid the movable grip 42 to raise or lower the load P, but in this system, the hoist control unit 100 receives a target position command or a speed command from the main control unit 110 and controls the drive motor 22. A control signal according to a program previously stored in the main control unit 110 is sent to the robot control unit 80, and the robot device 8 operates based on a control command based on this control signal.

[0117] 10, the fitting and assembling system 10 uses the lifting device 9 to chuck the workpiece Wa placed on the placement surface S. At this time, the hoisting machine 1 uses position control to stop the lifting device 9 at a position where the workpiece Wa will be chucked, and the robot device 8 remains stopped. The locking mechanism 92f of the hanging member 92 remains in the released state, and the chuck mechanism 91a of the clamping member 91 clamps the workpiece Wa from the left and right, chucking the workpiece Wa so that it can be lifted.

[0118] In step S24, the fitting and assembling system 10 uses the hoisting machine 1 to hoist the lifting device 9 and raise the workpiece Wa. At this time, the hoisting machine 1 uses position control to lift the workpiece Wa to a predetermined height and then lifts it off the ground, and then measures the load on the upper hook 3 using the load sensor 26. The predetermined height is the minimum height at which the workpiece Wa can be reliably lifted off the ground.

[0119] After lifting, the position of the robot linking member 92e is displaced closer to the base member 92a than the midpoint between the base member 92a and the top member 92b, but it is not in contact with the base member 92a. The hoist control unit 100 stores the set load WlO (N) or the reference torque TmO (Nm) calculated from the set load WlO (N) in memory 100a based on the load measured with the drive motor 22 stopped after lifting, and switches to normal float mode. During this time, the robot device 8 remains stopped, the locking mechanism 92f of the suspending member 92 remains released, and the chuck mechanism 91a of the clamping member 91 remains fastened, clamping the workpiece Wa from the left and right. Therefore, when lifting with the hoist 1, the robot device 8 is stopped, and the robot linking member 92e held by the hand unit 86h is stationary between the base member 92a and the top member 92b, so that the vertical load of the hoisting device 9 and the workpiece Wa is not acting on the robot device 8.

[0120] In step S25, the fitting and assembling system 10 switches the locking mechanism 92f of the hanging member 92 from the released state to the fastened state, and then transports the hoisting device 9 with the workpiece Wa chucked to a position where the fitting and assembling work will be performed, as shown in FIG. 11 . At this time, the hoisting machine 1 is normally operating in float mode, so the robot device 8 transports the hoisting device 9 in three dimensions along a predetermined path. The hoisting machine control unit 100 detects the operating force in the lifting and lowering direction that the robot device 8 applies to the hoisting device 9, and controls the torque of the drive motor 22 to follow the operation of the robot device 8, thereby winding up and down the load chain C1. In the horizontal direction, the hoisting machine 1 follows the horizontal movement of the hoisting device 9 due to the action of the crane 7, and moves directly above the hoisting device 9.

[0121] 12, in step S26, the fitting assembling system 10, in response to the fact that the workpiece Wa has reached the fitting assembling start position for the fitted workpiece Wb due to the operation of the robot device 8, makes the robot device 8 wait at that position. After this, the locking mechanism 92f of the hanging member 92 is switched to the released state, and then the hoisting machine 1 transitions to the fitting assembling float mode.

[0122] In step S27, the fitting assembling system 10 fits the workpiece Wa into the workpiece Wb to be fitted, as shown in Fig. 13. At this time, the robot device 8 remains stopped, the locking mechanism 92f of the hanging member 92 remains released, and the chuck mechanism 91a of the clamping member 91 remains fastened. Because the hoist 1 is in the fitting assembling float mode, the workpiece Wa descends at an extremely slow speed without any external force. The descending workpiece Wa fits into the fitting portion of the workpiece Wb to be fitted.

[0123] In step S27, if the fitting operation does not proceed smoothly and the lower surface of the workpiece Wa cannot be lowered until it is in close contact with the upper surface Wbs of the workpiece Wb, and fitting is not possible, the operation of step S28 is performed. If the fitting operation is completed, the operation of step S29 is performed without performing step S28.

[0124] In step S28, the fitting assembling system 10 performs the fitting work with the help of the worker when the direct teach mode switch 51b is turned on by the worker. At this time, the hoisting machine 1 maintains the fitting assembling float mode, and the robot device 8 transitions to the direct teach mode. The locking mechanism 92f of the hanging member 92 maintains the released state, and the chuck mechanism portion 91a of the clamping member 91 maintains the fastened state.

[0125] The direct teach mode of the robot device 8 is a mode in which the robot device 8 moves by following the movements of the worker. As a result, when the worker moves the workpiece Wa or the lifting device 9 back and forth or left and right in small increments to fit the workpiece Wa, the force sensor 86s detects the movement, and the robot device 8 moves accordingly. Therefore, the robot device 8 does not resist the force of the worker and does not interfere with the work. It is preferable that the force sensor 86s is provided on the robot connecting member 92e, and the worker's operation acts on the lifting device 9 via the force sensor 86s. While the worker is changing the position and orientation of the workpiece Wa, when the position and orientation of the workpiece Wa enter a range in which fitting is possible and the conditions for fitting are met, the lifting device 9 resumes its descent, and fitting and assembly automatically proceeds until the bottom surface of the workpiece Wa comes into close contact with the top surface Wbs of the workpiece Wb.

[0126] When the fitting and assembling of the workpieces Wa and Wb is completed by the worker's actions, the operation of step S29 is performed.

[0127] In step S29, the fitting and assembling system 10 detects that the fitting and assembling work of the workpieces Wa and Wb has been completed when the worker turns on the completion switch 51c. At this time, the hoisting machine 1 switches to position control, and the robot device 8 ends direct teach mode, switches to automatic operation, and waits in a stopped state. The locking mechanism 92f of the hanging member 92 remains in the released state, and the chuck mechanism 91a of the clamping member 91 switches to the open state. After the hoisting device 9 releases the workpiece Wa, the hoisting machine control unit 100 controls the drive motor 22 using position control to raise the hoisting device 9 to a predetermined height.

[0128] In step S30, the fitting and assembling system 10 moves the lifting device 9 to the position of the next workpiece Wa. At this time, the hoisting machine 1 sets a new set load W10 (N) and switches to normal float mode. Once the locking mechanism 92f of the hanging member 92 has been switched to the fastened state, the robot device 8 moves the lifting device 9 to the next work position. The hoisting machine 1 suspended by the crane 7 raises and lowers the lifting device 9 to follow the vertical movement of the lifting device 9 being transported by the robot device 8, and the crane 7 moves the lifting device 9 horizontally together with the hoisting machine 1 to follow the horizontal movement of the lifting device 9. The hoisting machine 1 and crane 7 move the lifting device 9 and workpiece Wa in three dimensions to assist the transport operation of the robot device 8.

[0129] In this manner, the fitting operation is performed by the fitting and assembling system 10.

[0130] [Fitting Assembly System 20] Next, a fitting assembly system 20 will be described, which is a modified example of the fitting assembly system 10. The main configuration of the fitting assembly system 20 is similar to that of the fitting assembly system 10, and therefore the fitting assembly system 20 will be described mainly with reference to FIG.

[0131] In the fitting assembly system 10, in order to fit and assemble the workpiece Wa, which is the part to be fitted and assembled, onto the top surface of the workpiece Wb, which is the part to be fitted and assembled, the fitting assembly mode is switched to directly above the workpiece Wa, and the workpiece Wa is placed on the workpiece Wb for assembly so that a pressing load Pa is applied from above.

[0132] In contrast, in the fitting assembly system 20, the workpiece Wa placed on a placement surface (not shown) is gripped and lifted by the lifting device 9, the hoisting machine control unit 100 is switched to normal float mode, and the robot device 8 moves the lifting device 9 to just above the target transfer position. Thereafter, by placing the workpiece Wa from above on the placement surface of a placement unit (not shown) in the fitting assembly mode, the transported workpiece Wa can be placed without impact even on an unstable placement surface.

[0133] In the fitting assembling system 20, the fitting assembling mode is not necessarily required; the robot device 8 moves the hoisting device 9 to directly above the position where the workpiece Wa to be transported is to be placed, and then the locking mechanism 92f of the hoisting device 9 is released. Next, the hoisting machine control unit 100 controls the position or speed to drive and control the drive motor 22 to lower the hoisting device 9, and the workpiece Wa to be transported is placed at the placement location. The method for lifting the load to be transported is the same as the method for lifting the workpiece Wa in the fitting assembling system 10, and therefore will not be described here.

[0134] The lifting device 9 has been described as an example in which the clamping members 91 clamp the sides of the workpiece Wa to be lifted, but the device that detachably holds the workpiece Wa to be assembled is not limited to the clamping members 91. It can be changed to a suction pad or other load-removal device depending on the shape of the workpiece Wa to be transported. Furthermore, if priority is given to reducing the time required to place the workpiece Wa to be transported over positional accuracy, it is preferable to switch the robot device 8 to direct teach mode just before the workpiece Wa to be transported lands so that the robot device 8 can follow changes in posture, etc., that accompany the landing of the workpiece Wa to be transported.

[0135] [Effects] According to the above embodiment, the following effects are achieved.

[0136] In the following description, "work" (no symbol) is a conceptual term that encompasses the load P, the upper fitting member 121, and the work Wa, and "work Wa" (with symbol) is a term that refers to the specific work Wa.

[0137] The hoist 1 lifts and lowers a workpiece (load P, upper fitting member 121 or workpiece Wa) by winding up or down a load chain C1 or rope from the hoist main body 2, and includes a load sheave 25 disposed on the hoist main body 2, around which the load chain C1 or rope is wound, and which winds up or down the load chain C1 or rope in response to rotation, a drive motor 22 which generates a driving force to rotate the load sheave 25, and a load (measurement load W1 or load torque) applied to the load sheave 25 via the load chain C1 or rope that suspends the workpiece (load P, upper fitting member 121 or workpiece Wa). The hoist control unit 100 has a normal float mode (first torque control mode) in which the torque of the drive motor 22 is controlled based on the load (measured load Wl or load torque Tl) output by the load calculation unit 100b and a predetermined reference load (set load Wl0 or reference torque Tm0), and a placement (fitted assembly) float mode (second torque control mode) in which the torque of the drive motor 22 is controlled to be a torque that is a predetermined amount (torque value corresponding to the pressing load Pa) smaller than that in the normal float mode (first torque control mode).

[0138] As a result, when the work (load P, upper fitting member 121, or workpiece Wa) suspended by the hoist 1 is lowered and placed on the placement surface, the pressing load Pa on the placement surface can be controlled to a predetermined load. Therefore, if the work (load P, upper fitting member 121, or workpiece Wa) is a member to be assembled (upper fitting member 121), when this member is lowered to the assembly section (lower fitting member 131) where the work is to be assembled and the two are assembled, the winding-down control for assembly can be optimized by switching from the first torque control mode of the normal float mode to the second torque control mode of the placement float mode. That is, in the normal float mode, the reaction force generated when the upper fitting member 121 comes into contact with the lower fitting member 131 cancels out the operating force, and the upper fitting member 121 cannot be brought into close contact with the lower fitting member 131. For this reason, if the workpiece (load P, upper fitting member 121, or workpiece Wa) is heavy, it is difficult to stop the shaking once it begins to sway. By using the loading float mode, alignment of the workpiece (load P, upper fitting member 121, or workpiece Wa) can be easily performed while applying an appropriate pressing load Pa. The upper fitting member 121 can be temporarily placed on the mounting surface of the attachment part while applying a pressing load Pa that allows for positioning and posture adjustment, and in this state fine adjustments of the position and posture can be easily made, and no skill is required to operate the hoist.

[0139] In addition, in the normal float mode (first torque control mode), the hoist control unit 100 sets the reference load (set load WlO or reference torque TmO) by the load value (measured load Wl or load torque Tl) calculated when the normal float mode (first torque control mode) is started, and controls the torque of the drive motor 22 based on the load value (measured load Wl or load torque Tl) and the reference load value (set load WlO or reference torque TmO). In the placement (fitting and assembly) float mode (second torque control mode), the hoist control unit 100 sets the reference load (set load WlO or reference torque TmO) to be smaller by a predetermined amount (a value corresponding to the pressing load Pa) than the load (measured load Wl or load torque Tl) calculated when the placement float mode (second torque control mode) is started, and controls the torque of the drive motor 22 based on the load value (set load WlO or reference torque TmO) and the reference load value (measured load Wl or load torque Tl). The torque of the drive motor 22 is controlled based on either the reference load (set load WlO or reference torque TmO) being set to the load value (measured load Wl or load torque Tl) calculated when the placement float mode (second torque control mode) is started, and a value larger than the load (set load WlO or reference torque TmO) by a predetermined amount (a value corresponding to the pressing load Pa) and the reference load value (measured load Wl or load torque Tl), or the reference load (set load WlO or reference torque TmO) is set to be smaller than the load (measured load Wl or load torque Tl) calculated when the placement float mode (second torque control mode) is started by a predetermined amount (a torque value corresponding to the pressing load Pa1), and the torque of the drive motor 22 is controlled based on the reference load (set load WlO or reference torque TmO) being set to be smaller than the load (measured load Wl or load torque Tl) calculated when the placement float mode (second torque control mode) is started by a predetermined amount (a torque value corresponding to the pressing load Pa2: Pa = Pa1 + Pa2).

[0140] This allows the basic logic part of the control flow used in both float modes to be standardized simply by changing the method of setting the reference load or measurement load when starting the first torque control mode and the second torque control mode, i.e., when starting the normal float mode and the placed (fitted assembly) float mode, thereby preventing the hoist control unit 100 from becoming complicated and reducing the control load.

[0141] Furthermore, when the load of the workpiece (load P, upper fitting member 121 or workpiece Wa) is known, in the normal float mode (first torque control mode), the hoist control unit 100 sets the reference load (set load WlO or reference torque TmO) to a value calculated from the known load, or sets it to a torque value corresponding to the known load, and controls the torque of the drive motor 22 based on the value of the reference load (set load WlO or reference torque TmO) and the value of the load (measured load Wl or load torque Tl), and in the placement (fitting and assembly) float mode (second torque control mode), the reference load (set load WlO or reference torque TmO) is set to be smaller by a predetermined amount (a value corresponding to the pressing load Pa) than the value calculated from the known load, and controls the torque of the drive motor 22 based on the value of the load and the reference load (set load WlO or reference torque TmO). Alternatively, the reference load (set load WlO or reference torque Tm0) is set to a value calculated from a known load, and the torque of the drive motor 22 is controlled based on a value that is larger than the load by a predetermined amount (a value corresponding to the pressing load Pa) and the value of the reference load (set load WlO or reference torque Tm0). Alternatively, the reference load (set load WlO or reference torque Tm0) is set to be smaller than the value calculated from the known load by a predetermined amount (a value corresponding to the pressing load Pa1), and the torque of the drive motor 22 is controlled based on a value that is larger than the load by a predetermined amount (a torque value corresponding to the pressing load Pa2: Pa = Pa1 + Pa2).

[0142] As a result, when the load of the component is known, i.e., when the load of the workpiece (load P or upper fitting member 121 or workpiece Wa) is known in advance, there is no need to measure and calculate the reference load when starting the normal float mode and the placement (fitting and assembly) float mode, so there is no need to measure the reference load every time the float mode is used, further reducing the control load.

[0143] In addition, the hoist control unit 100 can perform feedback control so that the deviation between the reference load (set load Wl0 or reference torque Tm0) and the load becomes zero.

[0144] This allows torque control in float mode by feedback control, which makes the control more complex than feedforward control, but allows for more precise and smooth fitting work. Note that the reference torque Tm0 is the target value on the input side in feedback control, and the load torque Tl is a value that is fed back in accordance with the value of the measured load.

[0145] In the normal float mode (first torque control mode) and the installation (fitted assembly) float mode (second torque control mode), the torque command value Tm is calculated based on the difference between the value of the reference load (set load WlO or reference torque value TmO) and the value of the load (measured load Wl or load torque value Tl), and the torque of the drive motor 22 is controlled.

[0146] This allows a torque command to be generated using (Equation 1) to (Equation 7) based on changes in tension acting on the load chain C1, and without the need for complex control, the work (load P, upper fitting member 121 or work Wa) lifted by the hoist 1 can be placed on the loading surface with a pressing load Pa appropriate for each work (load P, upper fitting member 121 or work Wa).

[0147] The fitting and assembling system 10 includes a hoist 1 that raises and lowers a workpiece (load P, upper fitting member 121, or workpiece Wa) by winding up and down a load chain C1 or rope from the hoist main body 2, a hoisting device 9 that is connected to the lower end of the load chain C1 or rope and holds the workpiece (load P, upper fitting member 121, or workpiece Wa) from above, a robot device 8 that is connected to the hoisting device 9 and moves the hoisting device 9, and a crane 7 that causes the hoisting device 1 to follow and be positioned above the hoisting device 9 as the hoisting device 9 moves horizontally, and the hoisting device 1 is arranged on the hoist main body 2, has the load chain C1 or rope wound around it, and has a load sheave 25 that winds up and lowers the load chain C1 or rope in response to its rotation, a drive motor 22 that generates a driving force to rotate the load sheave 25, and a robot device 8 that drives the hoisting device 9. The hoist 1 is provided with a load calculation unit 100b that calculates the load applied to the load sheave 25 via the load chain C1 or rope being lowered, and a hoist control unit 100 that controls the torque of the drive motor 22 based on the load, and the hoist control unit 100 has a normal float mode (first torque control mode) that controls the torque of the drive motor 22 based on a reference torque Tm0 corresponding to a predetermined reference load and a load torque Tl corresponding to the load, and a loading float mode (second torque control mode) that controls the torque of the drive motor 22 to be a torque that is a predetermined amount (torque value corresponding to the pressing load Pa) smaller than that in the normal float mode (first torque control mode), and when an operation is performed to lower a workpiece (load P, upper fitting member 121 or workpiece Wa) suspended by the hoist 1 toward a loading surface S on which the workpiece is to be placed, the loading float mode (second torque control mode) is selected by the hoist control unit 100.

[0148] As described above, the operation of lowering the workpiece (load P, upper fitting member 121, or workpiece Wa) suspended by the hoist 1 toward the placement surface S on which it is placed is specifically the operation of lowering the workpiece (load P, upper fitting member 121, workpiece Wa, or hoisting device 9) suspended by the hoist 1 toward the placement surface S. More specifically, in the operation of lowering the workpiece toward the placement surface S of a platform or the like, the placement surface S of the lower fitting member 131, or the placement surface S of the workpiece (load P, upper fitting member 121, or workpiece Wa) lifted by the hoisting device 9, and placing it on each placement surface, the placement (fitting and assembly) float mode (second torque control mode) is selected, including the operation of assembling or connecting the workpiece after placement.

[0149] As a result, even in the fitting and assembling system 10 including the hoist 1, the lifting device 9, the robot device 8, and the crane 7, when the upper fitting member 121 suspended by the hoist 1 is lowered onto the lower fitting member 131 placed on an assembly table or the like to assemble the two, torque control can be performed in the fitting and assembling float mode to optimize control. In other words, it is possible to suppress the impact when the upper fitting member 121 is placed on the upper surface of the lower fitting member 131, and it is easy to make fine adjustments for assembly after placement, making it easy to operate the hoist for assembly work.

[0150] In addition, the method of using the assembly system 10 includes the steps of setting the hoisting machine control unit 100 to normal float mode (first torque control mode) and holding the work (load P, upper fitting member 121 or work Wa) with the lifting device 9, moving the hoisting machine 1 above the lifting device 9 with the robot device 8 while using the crane 7 to follow the hoisting machine 1 above the lifting device 9, and moving the work (load P, upper fitting member 121 or work Wa) to just above the loading surface S, and setting the hoisting machine control unit 100 to loading (fitting and assembly) float mode (second torque control mode) while the robot device 8 is stopped, and lowering the work (load P, upper fitting member 121 or work Wa) toward the loading surface S in the loading (fitting and assembly) float mode (second torque control mode).

[0151] As a result, the workpiece Wa suspended by the hoist 1 can be transported to an assembly position for the workpiece Wb placed on the mounting surface of the mounting table or on the ground, and then the placement or assembly work can be performed. Therefore, using the fitting and assembling system 10 equipped with the robot device 8 and the crane 7, the transport work of various works (load P, upper fitting member 121 or workpiece Wa) can be performed appropriately according to the work, and the work efficiency can be improved.

[0152] The fitting assembly system 20 includes a hoist that raises and lowers a load P by winding up and down a load chain C1 or rope, a hoisting device 9 that is connected to the lower end of the load chain C1 or rope with a suspending member 92 and holds the load P from above, a robot device 8 that is connected to the hoisting device 9 and moves the hoisting device 9, and a crane 7 that causes the hoisting device 1 to follow and be positioned above the hoisting device 9 as the hoisting device 9 moves horizontally. The hoisting device 1 is disposed in the hoisting device main body 2, and has the load chain C1 or rope wound around it. The load sheave 25 winds up and lowers the load chain C1 or rope in response to its rotation. The drive motor 22 generates a driving force that rotates the load sheave 25. The load sheave 25 is attached to the load sheave 25 via the load chain C1 or rope that suspends the hoisting device 9. The hoisting device 9 includes a load sensor 26 that calculates the load torque Tl, a position calculation unit 100c that calculates the payout length of the load chain C1 or rope from the load sheave 25, and a hoisting machine control unit 100 that controls the drive motor 22 based on the load calculated by the load sensor 26, and the hoisting machine control unit 100 has a position control mode that performs position control based on the payout length calculated by the position calculation unit 100c.The hoisting device 9 includes a hanging member 92, a clamping member 91 that is connected to the lower part of the hanging member 92 and that is capable of detachably engaging with a workpiece (load P, upper fitting member 121 or workpiece Wa), a holding part 92g that is supported by the robot device 8, a robot connecting member 92e that guides the holding part 92g so that it can slide up and down relative to the hanging member 92 and the clamping member 91, and a locking mechanism 92f that fixes the holding part 92g to the robot connecting member 92e.

[0153] As a result, even in the fitting and assembling system 20 including the hoist 1, the lifting device 9, the robot device 8, and the crane 7, the load P suspended by the hoist 1 can be transported to a destination and placed thereon. A commercially available tool changer or the like can be utilized for the hand unit 86h provided on the wrist unit 86 of the robot device 8, and the load can be transported by connecting to the lifting device 9 suspended from the hoist 1.

[0154] In addition, the work (load P, upper fitting member 121 or work Wa) is the upper fitting member 121, and in the operation of lowering the upper fitting member 121 toward the mounting surface 131s of the lower fitting member 131, a mounting (fitting and assembly) float mode (second torque control mode) can be selected.

[0155] This makes it possible to provide a hoist 1 and fitting assembly systems 10, 20 that are optimal for assembly work, particularly fitting assembly work.

[0156] In the fitting assembly operation, if the position and orientation of the mating parts are outside the range in which they can be fitted, the fitting operation cannot be performed. On the other hand, since the position and orientation cannot be determined visually, fitting assembly must be attempted repeatedly by feel. However, when fitting assembly is performed in the fitting float mode, as soon as the position and orientation of the mating parts enter the range in which they can be fitted, the upper fitting member 121 resumes its descent, which had been stopped by the action of the pressing force Pa, and the fitting assembly proceeds automatically. Therefore, fitting assembly does not require skill.

[0157] The hoist control unit 100 has a normal float mode (first torque control mode) that controls the torque of the drive motor 22 based on the load and a predetermined reference load, and a mounted (fitted assembly) float mode (second torque control mode) that controls the torque of the drive motor 22 so that the torque is smaller than that in the normal float mode (first torque control mode).

[0158] As a result, even in the fitting and assembling system 20 including the hoist 1, the lifting device 9, the robot device 8, and the crane 7, when the load P or the upper fitting member 121 suspended by the hoist 1 is lowered and placed on the placement surface, the pressing load Pa on the placement surface can be controlled to a predetermined load. Therefore, when the load P is a member to be assembled (the upper fitting member 121), the member is lowered onto the assembly section (the lower fitting member 131) where the load P is to be assembled, and the two are assembled, the lowering control for assembly can be optimized by switching from the first torque control mode of the normal float mode to the second torque control mode of the placement float mode. That is, in the normal float mode, the reaction force generated by the upper fitting member 121 contacting the lower fitting member 131 cancels out the operating force, preventing the upper fitting member 121 from coming into close contact with the lower fitting member 131. Therefore, when the member to be assembled is heavy, it is difficult to stop the swinging once it starts to swing. By using the loading float mode, an appropriate pressing load Pa can be set for assembling the upper fitting member 121 or for aligning the load P on the loading surface, and the upper fitting member 121 can be placed on the assembly portion, and the load P can be placed on the loading surface S with a predetermined pressing load Pa applied thereto. This makes it easy to fine-tune the position and posture after loading or to connect the load to the loading surface, and no skill is required to operate the hoist.

[0159] The above-described embodiments each show a preferred specific example of the present invention. The numerical values, components, arrangement positions of the components, order of connection, etc. shown in the above-described embodiments are merely examples and are not intended to limit the present invention. Furthermore, the drawings are not necessarily strict illustrations.

[0160] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0161] For example, in the above embodiment, the motor torque commanded to the driver 27 in the fitting assembly float mode is calculated using various calculation methods, but this motor torque only needs to be slightly lower than the motor torque set in the normal float mode. The appropriate amount of reduction in motor torque differs depending on the pressing force required for each assembly or transport operation, so it is preferable to be able to set it individually for each operation.

[0162] In addition, in the above embodiment, the units of load and operating force are Newton (N), and torque is Newton-meter (Nm), but various calculations may be performed using other units as long as all values ​​use the same unit system.

[0163] Furthermore, in the above embodiment, a case has been described in which the second torque control mode is selected by the hoist control unit 100 (motor control means) during the assembly work of lowering the load P (member) suspended by the hoist 1 and assembling it to the lower fitting member 131 (lower member). However, the present invention can be applied to various work other than the assembly work of lowering the load P (member) and assembling it to the lower fitting member 131 (lower member), as long as the work is to lower the load P (member) toward a placement surface.

[0164] Furthermore, in the above embodiment, the surface on which the upper fitting member 121 and the load P are placed has been described as a placement surface, but the placement surface may be a member such as the lower fitting member 131, or if the loads P are stacked, it may be the top surface of the load P placed underneath, or it may be any surface such as a floor surface, a work surface, a table top surface, or a shelf, as long as it is a surface on which not only the load P but also the work (upper fitting member 121 or work Wa) lifted by the hoist 1 is placed. The placement surface does not need to be a flat surface, and may be a virtual surface or a set of points on which a load can be placed.

[0165] Furthermore, in the above embodiment, the crane 7 is exemplified as an unpowered overhead crane, but it may also be a powered crane such as a travel drive motor, and may also be a jib crane or any other moving device capable of moving the hoisting machine 1 horizontally.

[0166] DESCRIPTION OF SYMBOLS 1 Hoist 2 Hoist main body (hoist main body) 7 Crane 8 Robot device 9 Lifting device (holding means) 10 Fitting assembly system (hoisting system) 20 Fitting assembly system (hoisting system) 22 Drive motor 25 Load sheave (hoisting means) 26 Load sensor (load calculation means) 91 Clamping member (engagement mechanism) 92 Hanging member (connecting member) 92e Robot connecting member (guide member) 92f Lock mechanism (fixing mechanism) 92g Holding unit (robot support member) 100 Hoisting machine control unit (motor control means) 100b Load calculation unit (load calculation means) 100c Position calculation unit (position calculation means) 121 Upper fitting member (member) 131 Lower fitting member (lower member) 131s Placement surface C1 of lower fitting member Load chain P load

Claims

1. A hoist that raises and lowers a workpiece by winding up and down a load chain or rope from a hoist main body, comprising: hoisting means that is arranged on the hoist main body, around which the load chain or rope is stretched, and which winds up and lowers the load chain or rope in response to rotation; a drive motor that generates a driving force to rotate the hoisting means; load calculation means that calculates the load applied to the hoisting means via the load chain or rope that suspends the workpiece; and motor control means that controls the drive motor, wherein the motor control means has a first torque control mode that controls the torque of the drive motor based on the load output by the load calculation means and a predetermined reference load, and a second torque control mode that controls the torque of the drive motor so that the torque is a predetermined amount smaller than that in the first torque control mode.

2. A hoist as claimed in claim 1, characterized in that the motor control means, in the first torque control mode, sets the reference load according to the load value calculated when the first torque control mode is started, and controls the torque of the drive motor based on the load value and the reference load value; and, in the second torque control mode, sets the reference load to be a predetermined amount smaller than the load calculated when the second torque control mode is started, and controls the torque of the drive motor based on the load value and the reference load value, or sets the reference load to the load value calculated when the second torque control mode is started, and controls the torque of the drive motor based on a value larger than the load by a predetermined amount and the reference load value; or sets the reference load to be a predetermined amount smaller than the load calculated when the second torque control mode is started, and controls the torque of the drive motor based on a value larger than the load by a predetermined amount and the reference load value.

3. A hoist as claimed in claim 1, characterized in that, when the load of the workpiece is known, in the first torque control mode, the motor control means sets the reference load to a value calculated from the known load, or sets it to a torque value corresponding to the known load, and controls the torque of the drive motor based on the value of the reference load and the value of the load; and in the second torque control mode, sets the reference load to a value smaller than the value calculated from the known load by a predetermined amount, and controls the torque of the drive motor based on the value of the load and the value of the reference load, or sets the reference load to a value calculated from the known load, and controls the torque of the drive motor based on a value larger than the load by a predetermined amount and the value of the reference load; or sets the reference load to a value smaller than the value calculated from the known load by a predetermined amount, and controls the torque of the drive motor based on a value larger than the load by a predetermined amount and the value of the reference load.

4. A hoist as claimed in claim 1, characterized in that the motor control means performs feedback control so that the deviation between the reference load and the load becomes zero.

5. A hoist as claimed in claim 2 or 3, characterized in that in the first torque control mode and the second torque control mode, a torque command value is calculated based on the difference between the reference load value and the load value, and torque control of the drive motor is performed.

6. A hoist system comprising: a hoist that raises and lowers a workpiece by winding up and down a load chain or rope from a hoist main body; holding means connected to the lower end of the load chain or rope and holding the workpiece from above; a robot device connected to the holding means and moving the holding means; and a crane that causes the hoist to follow and position itself above the holding means as the holding means moves in the horizontal direction, wherein the hoist comprises: hoisting means that is disposed on the hoist main body and around which the load chain or rope is wound and that winds up and lowers the load chain or rope in response to rotation; a drive motor that generates a drive force that rotates the hoisting means; load calculation means that calculates the load applied to the hoisting means via the load chain or rope that suspends the holding means; and motor control means that controls the torque of the drive motor based on the load, wherein the motor control means has: a first torque control mode that controls the torque of the drive motor based on a reference torque corresponding to a predetermined reference load and a load torque corresponding to the load; and a second torque control mode that controls the torque of the drive motor so that the torque is a predetermined amount smaller than that of the first torque control mode, wherein the second torque control mode is selected by the motor control means during an operation of lowering the workpiece suspended by the hoist toward a placement surface on which the workpiece is placed.

7. A method of using a hoist system using the hoist system described in claim 6, comprising the steps of: setting the motor control means to the first torque control mode and holding the workpiece with the holding means; moving the holding means with the robot device while causing the hoist to follow above the holding means with the crane, thereby moving the workpiece to directly above the placement surface; and, with the robot device stopped, setting the motor control means to the second torque control mode and lowering the workpiece towards the placement surface in the second torque control mode.

8. A hoist system comprising: a hoist that raises and lowers a workpiece by winding up and down a load chain or rope from a hoist main body; holding means that is connected to the lower end of the load chain or rope with a connecting member and holds the workpiece from above; a robot device that is connected to the holding means and moves the holding means; and a crane that causes the hoist to follow and position itself above the holding means as the holding means moves in the horizontal direction, wherein the hoist comprises: hoisting means that is disposed on the hoist main body and around which the load chain or rope is wound and that winds up and lowers the load chain or rope in response to rotation; a drive motor that generates a drive force to rotate the hoisting means; load calculation means that calculates the load applied to the hoisting means via the load chain or rope that suspends the holding means; position calculation means that calculates the payout length of the load chain or rope from the hoisting means; and motor control means that controls the drive motor based on the load calculated by the load calculation means; the motor control means has a position control mode in which position control is performed based on the payout length calculated by the position calculation means, and the holding means comprises: the connecting member; an engagement mechanism connected to the lower part of the connecting member and adapted to detachably engage with the work; a robot support member supported by the robot device; a guide member that guides the robot support member so that it can slide vertically relative to the connecting member and the engagement mechanism; and a fixing mechanism that fixes the robot support member to the guide member.

9. A hoist as claimed in claim 1, characterized in that the work is an upper member, and the second torque control mode can be selected when lowering the upper member towards a support surface of a lower member.

10. A hoist system as described in claim 8, characterized in that the motor control means has a first torque control mode for controlling the torque of the drive motor based on the load and a predetermined reference load, and a second torque control mode for controlling the torque of the drive motor so as to be smaller than the torque in the first torque control mode.