Load control unit

Abstract

A load control unit (1) is retrofitted to a load generation device that generates a prescribed load, and applies additional braking force to the prescribed load, the load control unit (1) comprising a reel (11) that has a rotary shaft member (11a) and rotates around the rotary shaft member (11a), a magnetic viscous fluid device (14) that brakes the rotary shaft member (11a) by applying a magnetic field to a magnetic viscous fluid (14a), and a modulation unit that modulates the magnetic field applied to the magnetic viscous fluid (14a).

Description

Load Control Unit

[0001] The present invention relates to a load control unit.

[0002] Patent Document 1 discloses a training device that includes a load generating means that moves a weight upward.

[0003] Japanese Patent No. 3718211

[0004] However, with load generating devices that generate a predetermined load using weights, such as non-electrified training equipment, it is difficult to finely adjust the load. The present disclosure aims to provide a load control unit that can be retrofitted to a load generating device to adjust the load more precisely than conventional methods.

[0005] In order to solve the above problems, a load control unit according to one embodiment of the present invention is a load control unit that is retrofitted to a load generating device that generates a predetermined load and that applies additional braking force to the predetermined load, and is equipped with a reel that has a rotating shaft member and rotates around the rotating shaft member, a magnetorheological fluid device that brakes the rotating shaft member by applying a magnetic field to a magnetorheological fluid, and a modulation unit that modulates the magnetic field applied to the magnetorheological fluid.

[0006] According to one aspect of the present invention, the load can be adjusted more finely than before.

[0007] It is a schematic diagram showing the general configuration of a training system including a load control unit according to an embodiment of the present invention. It is a cross-sectional view of the load control unit as seen from the left side in the left-right direction. It is a cross-sectional view of the magnetorheological fluid device as seen from the left side in the left-right direction. It is a block diagram of the training system. It is a diagram showing the torque characteristics of the magnetorheological fluid device with respect to the coil current input to the coil of the magnetorheological fluid device.

[0008] Fig. 1 is a schematic diagram showing the overall configuration of a training system including a load control unit according to one embodiment of the present invention. The training system SYS shown in Fig. 1 includes a training apparatus 100, a load control unit 1, a support device 200, and a display device 30. The load control unit 1 and the support device 200 are attached to the training apparatus 100. Hereinafter, the up-down direction, the left-right direction, and the front-rear direction will be defined as shown in Fig. 1.

[0009] The training device 100 shown in FIG. 1 is an example of a load generating device, and employs a weight stack system, and includes a frame 101, a first cable 102, a pulley group 103, a weight stack 104, a lift shaft 105-1, a left guide shaft 105-2, and a right guide shaft 105-3.

[0010] The frame 101 is a skeleton that supports the weight stack 104. The frame 101 shown in FIG. 1 includes a right frame 101-1, an upper frame 101-2, a left frame 101-3, and a lower frame 101-4. The right frame 101-1 and the left frame 101-3 are pillars that extend in the vertical direction. The upper frame 101-2 connects the upper end of the right frame 101-1 to the upper end of the left frame 101-3. The lower frame 101-4 connects the lower end of the right frame 101-1 to the lower end of the left frame 101-3.

[0011] One end 102a of the first cable 102 is located outside the frame 101 of the training device 100. An attachment appropriate for the training to be performed by a user of the training device 100 (hereinafter simply referred to as the user) is connected to the one end 102a of the first cable 102. The training includes exercises for strengthening muscles and rehabilitation. The other end 102b of the first cable 102 is fixed to the upper frame 101-2. For example, by connecting a handle to the one end 102a of the first cable 102, the training device 100 functions as an adjustable pulley.

[0012] The pulley group 103 is arranged to smooth the movement of the first cable 102, and each pulley has a rotatable structure. The pulley group 103 shown in Figure 1 includes pulley 103-1, pulley 103-2, pulley 103-3, and pulley 103-4. The pulley 103-4 is a movable pulley that is hung on the first cable 102 and is connected to the tip of the lift shaft 105-1.

[0013] The weight stack 104 is an example of a load generating unit that generates a load. In the weight stack 104, multiple weight plates are stacked vertically along the left guide shaft 105-2 and the right guide shaft 105-3. The weight stack 104 is configured so that the load applied to the first cable 102 can be adjusted for each weight plate. In FIG. 1, a weight pin P is inserted into one of the multiple weight plates. The weight plate into which the weight pin P is inserted and the weight plate located above that weight plate are integrated with the lift shaft 105-1. Hereinafter, the weight plate integrated with the lift shaft 105-1 by the weight pin P will be referred to as the first weight.

[0014] When a user performs training by pulling the handle connected to one end 102a of first cable 102, a load equivalent to the weight plate integrated with lift shaft 105-1 is applied upward to one end 102a of first cable 102. When the user pulls down the handle against the load, first cable 102 is pulled out to the outside of training apparatus 100. Because the other end 102b of first cable 102 is fixed to upper frame 101-2, when first cable 102 is pulled out to the outside of training apparatus 100, pulley 103-4, lift shaft 105-1 connected to pulley 103-4, the first weight, and the weight plate arranged above the first weight are lifted upward.

[0015] A load control unit 1 is attached to the training device 100 directly below the weight stack 104. The load control unit 1 is attached to, for example, a non-electrified load generating device such as the training device 100, and is used to adjust the load applied to the user.

[0016] Users such as professional athletes who aim to increase muscle mass and improve explosive power through meticulous training plans desire the ability to precisely adjust the load used in their training. However, with non-electrical load generators such as the training device 100, it is difficult to adjust the load more precisely than the weight of the weight plates included in the weight stack 104, and this has sometimes prevented users from meeting their needs. The load control unit 1 adds a load that can be adjusted more precisely than the weight of the weight plates included in the weight stack 104 to the load generated by the weight stack 104, thereby enabling precise adjustment of the load applied to the user.

[0017] The display device 30 is, for example, an information terminal such as a tablet terminal or a smartphone. The display device 30 has at least a display unit, such as a liquid crystal display, that can display at least a screen used for operating the load control unit 1, and an operation member, such as a touch panel. The load control unit 1 and the display device 30 will be described later with reference to FIG. 3.

[0018] The support device 200 supports the display device 30 so that the display device 30 is positioned at a position desired by the user in a posture desired by the user. The support device 200 is attached to the left frame 101-3 of the training apparatus 100 via an attachment portion 201. An arm 202 is connected to the attachment portion 201. The arm 202 is, for example, an articulated arm, a flexible arm, or the like. A holding portion 203 is connected to the end of the arm 202 opposite the end attached to the attachment portion 201. The holding portion 203 has, for example, a storage portion 203-1 and a tilting portion 203-2. The storage portion 203-1 has a space inside that can store the display device 30. The tilting portion 203-2 is, for example, a two-axis hinge, and tilts the storage portion 203-1 with respect to the extension direction 202a of the arm 202. The user can move the arm 202 to place the display device 30 in a desired position, and use the tilting portion 203-2 to orient the housing portion 203-1 in a desired direction, thereby orienting the display device 30 in a desired direction.

[0019] The load control unit 1 can communicate wirelessly or wired with the display device 30. For example, the load control unit 1 can communicate with the display device 30 by short-range wireless communication such as Bluetooth (registered trademark).

[0020] Figure 2 is a cross-sectional view of load control unit 1 as viewed from the left side in the left-right direction. As shown in Figure 2, load control unit 1 includes reel 11, second cable 12, rotation detection unit 13, magnetorheological fluid device 14, and laser distance measuring device 19 inside unit case 17. Load control unit 1 also includes control device 15 housed inside protective case 18. Control device 15 is, for example, a semiconductor board equipped with a microcontroller.

[0021] The reel 11 has a rotary shaft member 11a and rotates around the rotary shaft member 11a. A second cable 12 is wound around the reel 11. The tip 12a of the second cable 12 is tied to a joint 12b. The second cable 12 is connected to the lower end of the lift shaft 105-1 via the joint 12b.

[0022] The rotation detector 13 detects the amount and direction of rotation of the rotating shaft member 11a. The rotation detector 13 is, for example, a rotary encoder, a magnetic sensor, or the like. When the lift shaft 105-1 rises, the rotating shaft member 11a rotates in the normal direction, and the second cable 12 is unwound from the reel 11. At this time, the rotation detector 13 transmits to the control device 15 a detection signal including information indicating that the rotating shaft member 11a has rotated in the normal direction and information indicating the amount of rotation.

[0023] The rotating shaft member 11a is biased in the reverse direction opposite to the normal rotation direction by a biasing member such as a spiral spring. When the magnetorheological fluid device 14 is not applying a braking force, the second cable 12 is wound onto the reel 11 by the biasing force of the biasing member.

[0024] The magnetorheological fluid device 14 has a magnetorheological fluid 14a and a container 14b that stores the magnetorheological fluid 14a. The magnetorheological fluid 14a has a characteristic that its viscosity changes depending on the strength of a magnetic field. The container 14b has an opening 14h on its side that faces the reel 11 in the front-to-rear direction. A portion 11b of the rotating shaft member 11a is inserted into the container 14b through the opening 14h.

[0025] FIG. 3 is a cross-sectional view of the magnetorheological fluid device 14 as viewed from the left side in the left-right direction. As shown in FIG. 3, the magnetorheological fluid device 14 includes the magnetorheological fluid 14a described above, the container 14b described above, the rotor 14c, the coil 14d, and the bearing 14e. The container 14b is composed of a container body 14b-1 and a cap 14b-2. The container body 14b-1 protects the internal components such as the rotor 14c. The cap 14b-2 is attached to the container body 14b-1 before the magnetorheological fluid 14a is injected into the container body 14b-1. The cap 14b-2 seals the container body 14b-1 so that the magnetorheological fluid 14a remains inside the container body 14b-1.

[0026] The rotor 14c is fixed to a portion 11b of the rotating shaft member 11a and rotates around the rotating shaft member 11a inside the container body 14b-1. The bearing 14e is disposed between the portion 11b of the rotating shaft member 11a and the container body 14b-1 and allows the portion 11b of the rotating shaft member 11a to rotate smoothly. The coil 14d generates a magnetic field M when a current flows through it. The magnetic field M generated by the coil 14d changes the viscosity of the magnetorheological fluid 14a, which changes the coefficient of friction between the rotor 14c and the magnetorheological fluid 14a. In other words, the magnetic field M controls the braking force generated as the rotating shaft member 11a rotates.

[0027] 1 is lifted upward, the second cable 12 connected to the lower end of the lift shaft 105-1 via the joint 12b is unwound from the reel 11. At this time, the load control unit 1 applies an additional load to the load due to the weight stack 104 by the magnetorheological fluid device 14 braking the rotation of the rotating shaft member 11a of the reel 11. Hereinafter, the load resulting from the weight stack 104 plus the braking force generated by the magnetorheological fluid device 14 will be referred to as the total load.

[0028] The laser distance measuring device 19 measures the distance to the first weight among the multiple weight plates included in the weight stack 104. The laser distance measuring device 19 is housed on the upper surface side of the unit case 17, and the laser light emitting surface and light receiving surface are exposed to the outside of the unit case 17.

[0029] 2 shows the weight plates that make up the weight stack 104, including the bottom weight plate 104-1, the second-lowest weight plate 104-2, and the third-lowest weight plate 104-3. The weight plates that make up the weight stack 104 each have a pin insertion hole into which a weight pin P can be inserted. For example, weight plate 104-1 has a pin insertion hole 104-1h, and weight plate 104-2 has a pin insertion hole 104-2h. In FIG. 2, the weight pin P is inserted into the pin insertion hole 104-2h of weight plate 104-2, and weight plate 104-2 is the first weight.

[0030] The lift shaft 105-1 has pin insertion holes 105-1h that correspond to the pin insertion holes 104-2h of the weight plates 104-2 that make up the weight stack 104. The weight pins P are inserted from the front openings of the pin insertion holes 104-2h of the weight plate 104-2, pass through the pin insertion holes 105-1h at positions corresponding to the weight plate 104-2, and reach the rear sides of the pin insertion holes 104-2h. This allows the weight plate 104-2 to become one with the lift shaft 105-1.

[0031] The laser light emitted from the light-emitting unit of the laser distance measuring device 19 is reflected by the weight pin P inserted into the pin insertion hole 104-2h of the weight plate 104-2 and enters the light-receiving unit of the laser distance measuring device 19. The laser distance measuring device 19 transmits to the control device 15 a signal indicating the phase difference between the laser light emitted from the light-emitting unit and the laser light incident on the light-receiving unit, the time difference between the time when the laser light is emitted from the light-emitting unit and the time when the laser light is incident on the light-receiving unit, or the angle difference between the laser light emitted from the light-emitting unit and the laser light incident on the light-receiving unit. The control device 15 is an example of an estimation unit, and acquires the distance between the laser distance measuring device 19 and the weight pin P based on the signal received from the laser distance measuring device 19, estimates the total weight of the first weight and the weight plate arranged above the first weight, and estimates the load caused by the weight stack 104. In the case of FIG. 2, the control device 15 estimates the total weight of the weight plate 104-2, which is the first weight, and the weight plates arranged above the weight plate 104-2, and estimates the load caused by the weight stack 104.

[0032] 4 is a block diagram of the training system SYS. As shown in FIG. 4, the load control unit 1 has a rotation detection unit 13, a magnetorheological fluid device 14, a laser distance measuring device 19, a first control unit 20, a communication unit 21, a main memory unit 22, an auxiliary memory unit 23, and a voltage conversion unit 24. The display device 30 has a second control unit 31, a display 32, a touch panel 33, a communication unit 34, a main memory unit 35, and an auxiliary memory unit 36.

[0033] The first control unit 20, communication unit 21, main memory unit 22, auxiliary memory unit 23, and voltage conversion unit 24 of the load control unit 1 are arranged in the control device 15. The first control unit 20 is realized, for example, by a central processing unit (CPU) or a microprocessing unit (MPU). The communication unit 21 is realized, for example, by a microcomputer for communication control, and performs short-range wireless communication with the display device 30. The main memory unit 22 is a volatile storage medium such as a random access memory (RAM). The auxiliary storage unit 23 is a non-volatile storage medium such as a read-only memory (ROM), a hard disk drive (HDD), or a flash memory. The first control unit 20 uses the main memory unit 22 as a working area and executes programs stored in the auxiliary storage unit 23 to control each component of the load control unit 1, such as the magnetorheological fluid device 14.

[0034] The voltage conversion unit 24 is an example of a modulation unit. Under the control of the first control unit 20, the voltage conversion unit 24 inputs a drive voltage to the magnetorheological fluid device 14. The voltage conversion unit 24 includes, for example, a voltage amplifier circuit using a transistor, and amplifies the DC voltage of the electrical signal output from the first control unit 20 to a drive voltage for the magnetorheological fluid device 14. For example, a grounded emitter circuit can be used as the voltage amplifier circuit using a transistor. The first control unit 20 controls the voltage conversion unit 24 to perform pulse width modulation on the drive electrical signal input to the magnetorheological fluid device 14.

[0035] By pulse-width modulating the drive electrical signal input to the magnetorheological fluid device 14, the input current to the coil 14d, which applies the magnetic field M to the rotor 14c, is also modulated. A back electromotive force is generated in the coil 14d at the timing of the rising and falling edges of the pulse width in the pulse-width modulation. The magnetorheological fluid device 14 may reduce the influence of the back electromotive force that is repeatedly generated in short cycles by connecting a diode in parallel with the coil 14d. The anode of the diode is electrically connected to the rotor-side terminal of the coil 14d.

[0036] The second control unit 31 is realized by, for example, a CPU or an MPU. The communication unit 34 is realized by, for example, a microcomputer for communication control, and performs short-range wireless communication with the load control unit 1. The main memory 35 is, for example, a volatile storage medium such as RAM. The auxiliary memory 36 is, for example, a non-volatile storage medium such as ROM, HDD, or flash memory. The second control unit 31 controls each unit of the display device 30 by using the main memory 35 as a working area and executing programs stored in the auxiliary memory 36.

[0037] The display 32 is, for example, a liquid crystal display or an organic EL display. The display 32 displays, for example, a setting screen used for operating the load control unit 1. The setting screen displayed on the display 32 is used, for example, to set parameters for determining the braking force to be applied by the magnetorheological fluid device 14. The parameters to be set include, for example, the magnitude of the braking force, the duty ratio, etc.

[0038] The touch panel 33 is, for example, a capacitance-type touch panel, and is an input device used in combination with the display 32. When the setting screen is displayed on the display 32, the user uses an input device such as the touch panel 33 to set parameters for determining the braking force to be applied by the magnetorheological fluid device 14. The touch panel 33 may be operated by an instructor who provides training guidance to the user. The first control unit 20 sets the duty ratio of the pulse width modulation to be applied to the drive electrical signal to the magnetorheological fluid device 14 based on the set parameters.

[0039] The duty ratio of the pulse width modulation is set to a discrete value in increments of a predetermined value. For example, the duty ratio is expressed by a k-digit bit string, and is 1 / 2 k The duty ratio can be set in increments of 1 / 2. k The change in braking force Δf applied by the magnetorheological fluid device 14 due to the change in the braking force is given as follows: Δf=(maximum braking force−minimum braking force) / 2 kHere, the maximum and minimum values ​​of the braking force are the maximum and minimum values ​​within the range of values ​​that the braking force exerted by the magnetorheological fluid device 14 can take.

[0040] The load control unit 1 controls the magnetorheological fluid device 14 so that the braking force can be adjusted more precisely than the load that can be adjusted by the weight plates 104-1 and the like included in the weight stack 104. For example, if the weight of the weight plates 104-1 and the like is on the order of 1 kg, the magnetorheological fluid device 14 is controlled so that the braking force can be adjusted on the order of 0.1 N or less. If the allowable error in the braking force is, for example, 5%, the braking force is adjusted to 0.005 N, so the number of digits k of the duty ratio is determined so that the amount of change in braking force Δf is on the order of 0.001 N or less.

[0041] The magnetic field M applied to the magnetorheological fluid 14a is modulated by pulse-width modulating the driving electric signal input to the magnetorheological fluid device 14. A change in viscosity occurs in the magnetorheological fluid 14a, which changes the coefficient of friction between the rotor 14c and the magnetorheological fluid 14a, and changes the braking force generated as the rotating shaft member 11a rotates.

[0042] 5 is a diagram showing the torque characteristics of the magnetorheological fluid device 14 relative to the coil current input to the coil 14d of the magnetorheological fluid device 14. In FIG. 5, a solid line 51 shows an example of the measured torque characteristics of the magnetorheological fluid device 14.

[0043] The first control unit 20 may set the duty ratio of the pulse width modulation applied to the driving electric signal to the magnetorheological fluid device 14 based on the duty ratio stored in the auxiliary storage unit 23. The duty ratio of the pulse width modulation applied to the driving electric signal to the magnetorheological fluid device 14 is measured in advance for each braking force to be applied by the magnetorheological fluid device 14 during the design stage of the load control unit 1 and stored in the auxiliary storage unit 23. Once the braking force to be applied by the magnetorheological fluid device 14 is determined, the first control unit 20 determines the torque value of the magnetorheological fluid device 14 required to apply the braking force and obtains the duty ratio corresponding to that torque value from the auxiliary storage unit 23. For example, the coil current when the torque value is T1 [N m] in the solid line 51 is I1 [A]. The first control unit 20 acquires the duty ratio when the coil current input to the coil 14d is I1 [A] from the auxiliary memory unit 23, and controls the voltage conversion unit 24 so that the driving electrical signal input to the magnetorheological fluid device 14 is modulated with the acquired duty ratio.

[0044] [Modifications] In the above embodiment, the load control unit 1 is attached to the weight stack type training apparatus 100. However, the load generating device to which the load control unit 1 is attached is not limited to the weight stack type training apparatus 100. For example, the load control unit 1 may be attached to a load generating device such as a plate loading type or a power rack type training apparatus.

[0045] Furthermore, the pulley 103-4 is not an essential component of the training device 100. If the training device 100 does not include the pulley 103-4, the other end 102b of the first cable 102 fixed to the upper frame 101-2 in FIG. 1 may be connected to the tip of the lift shaft 105-1.

[0046] In the above embodiment, the first control unit 20 of the control device 15 controls the voltage conversion unit 24 and the magnetorheological fluid device 14, but it may also be controlled by the second control unit 31, the communication control microcomputer of the communication unit 21, etc.

[0047] In the above embodiment, the voltage conversion unit 24 changes the duty ratio under the control of the first control unit 20 to perform pulse width modulation on the driving electric signal input to the magnetorheological fluid device 14. However, the modulation performed by the voltage conversion unit 24 on the driving electric signal input to the magnetorheological fluid device 14 may be a modulation method other than pulse width modulation, or may be a modulation method that is an improvement on pulse width modulation.

[0048] [Summary] The load control unit according to aspect 1 of the present invention is a load control unit that is retrofitted to a load generating device that generates a predetermined load and that applies additional braking force to the predetermined load, and is equipped with a reel that has a rotating shaft member and rotates around the rotating shaft member, a magnetorheological fluid device that brakes the rotating shaft member by applying a magnetic field to a magnetorheological fluid, and a modulation unit that modulates the magnetic field applied to the magnetorheological fluid.

[0049] According to the above configuration, by retrofitting the load control unit to the load generating device, it is possible to adjust the load more precisely than before. By being able to adjust the load more precisely, the user can easily realize that the load used in training is gradually increasing during daily training, and the user's motivation for training can be maintained.

[0050] A load control unit according to aspect 2 of the present invention is the same as that of aspect 1, wherein the modulation unit modulates the magnetic field applied to the magnetorheological fluid by pulse-width modulating the electrical signal input to the magnetorheological fluid device.

[0051] According to the above configuration, by pulse-width modulating the electrical signal input to the magnetorheological fluid device, the current value of the electrical signal input to the magnetorheological fluid device can be controlled with high precision. Furthermore, by employing pulse-width modulation to modulate the electrical signal input to the magnetorheological fluid device, it is possible to suppress the generation of ripple noise in the electrical signal input to the magnetorheological fluid device and to reduce power loss.

[0052] A load control unit according to aspect 3 of the present invention is configured such that, in aspect 2 above, the magnetorheological fluid device has a rotor fixed to a rotating shaft member 11a and a coil that generates a magnetic field to be applied to the magnetorheological fluid, and the load control unit further includes a memory unit that stores a duty ratio of the pulse width modulation corresponding to the additional braking force due to the magnetorheological fluid, and the modulation unit selects the duty ratio of the pulse width modulation stored in the memory unit according to a predetermined braking force due to the magnetorheological fluid.

[0053] When pulse-width modulation is performed on the electrical signal input to the magnetorheological fluid device, it is expected that the torque characteristics of the magnetorheological fluid device will change linearly with respect to the current flowing through the coil, but the actual torque characteristics may change nonlinearly. With the above configuration, the pulse-width modulation duty ratio can be selected based on the additional braking force provided by the magnetorheological fluid device stored in the memory unit. Therefore, even if the torque characteristics of the magnetorheological fluid device with respect to the current flowing through the coil change nonlinearly, an appropriate braking force can be applied. This allows users who aim to increase muscle mass and improve explosive power through meticulously planned training, like professional athletes, to train according to their plan with peace of mind.

[0054] A load control unit according to aspect 4 of the present invention is, in the above-mentioned aspect 2 or 3, such that the modulation unit sets the duty ratio of the pulse width modulation to a discrete numerical value in increments of a predetermined value, and the amount of change in the braking force applied by the magnetorheological fluid device as the duty ratio changes by the predetermined value is on the order of 0.1 N or less.

[0055] With a load generator that generates a predetermined load, it is difficult to adjust the load on the order of 0.1 N or less. With the above configuration, the load can be adjusted more finely than with conventional load generators.

[0056] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0057] REFERENCE SIGNS LIST 1 Load control unit 11 Reel 11a Rotating shaft member 12 Second cable 14 Magnetorheological fluid device 14a Magnetorheological fluid 14c Rotor 14d Coil 15 Control device 20 First control unit 21, 34 Communication unit 23 Auxiliary storage unit 24 Voltage conversion unit 30 Display device 31 Second control unit 32 Display 33 Touch panel 100 Training equipment

Claims

1. A load control unit that is retrofitted to a load generating device that generates a specified load and that applies additional braking force to the specified load, comprising: a reel having a rotating shaft member that rotates around the rotating shaft member; a magnetorheological fluid device that brakes the rotating shaft member by applying a magnetic field to a magnetorheological fluid; and a modulation unit that modulates the magnetic field applied to the magnetorheological fluid.

2. A load control unit according to claim 1, wherein said modulation section modulates the magnetic field applied to said magnetorheological fluid by pulse-width modulating an electrical signal input to said magnetorheological fluid device.

3. A load control unit as described in claim 2, wherein the magnetorheological fluid device has a rotor fixed to a rotating shaft member and a coil that generates a magnetic field to be applied to the magnetorheological fluid, and the load control unit further has a memory unit that stores a duty ratio of the pulse width modulation corresponding to the additional braking force by the magnetorheological fluid, and the modulation unit selects the duty ratio of the pulse width modulation stored in the memory unit according to a predetermined braking force by the magnetorheological fluid.

4. A load control unit as described in claim 2, wherein the modulation section sets the duty ratio of the pulse width modulation to a discrete value in increments of a predetermined value, and the amount of change in the braking force applied by the magnetorheological fluid device as the duty ratio changes by the predetermined value is on the order of 0.1 N or less.

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