A brush motor resistance control circuit, control method and fitness training device

Abstract

The present application relates to the technical field of brush motor control, and particularly relates to a brush motor resistance control circuit, a control method and a fitness training device. The brush motor resistance control circuit comprises a control switch and an adjustable load. The control switch receives a control signal and controls the on-off of the circuit. The control switch comprises a first switch, a second switch, a third switch and a fourth switch. The second switch and the fourth switch are connected to the other end of the adjustable load, and the other ends of the second switch and the fourth switch are connected to a capacitor in parallel. The resistance of the brush motor during rotation is controlled. Compared with a brushless motor, the brush motor does not need to be separately increased in commutation control, so that the control difficulty of the brush motor is reduced. The resistance of the brush motor is dynamically adjusted by adjusting the resistance of the brush adjustable load.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of brush motor control, and particularly relates to a brush motor resistance control circuit, a control method and a fitness training device. BACKGROUND

[0002] At present, brush motors are widely used in the market and have low cost. The brush motor can directly output direct current when used as a generator, and does not need rectification and high-precision control, so the cost is low. With the progress of society, people pay more attention to health and fitness, and the demand for exercise is obviously increasing. Due to time, space and other factors, people's demand for indoor fitness and simulation training has greatly increased. Therefore, the demand for fitness devices such as indoor cycling training tables, rowing machines and strength stations is also very large. Indoor fitness devices provide resistance to the human body to achieve the process of simulating the human body to do corresponding actions to do work outside when exercising outdoors. The resistance is generated in many ways, for example, some fitness equipment uses the weight of heavy objects as a resistance source, and through various mechanisms, the user lifts the heavy objects when doing actions to achieve resistance. For example, some fitness equipment uses electromagnets or permanent magnets to drive the conductors to move relative to the magnets, and the conductors generate eddy currents under the internal magnetic field to generate resistance. Some fitness equipment uses three-phase brushless motors / generators to generate resistance.

[0003] There are many types of existing resistance generation technologies:

[0004] Counterweight resistance: uses the gravity of counterweight heavy objects as simulated resistance. Disadvantages: poor dynamic adjustment capability, large system volume, heavy weight, and inconvenience for digitization and intelligentization.

[0005] Water resistance: the user moves to stir the water in the water tank to achieve simulated resistance. Disadvantages: poor dynamic adjustment capability, large system volume, heavy weight after adding water, and inconvenience for digitization and intelligentization.

[0006] Wind resistance: the user moves to stir the fan blades to blow wind to achieve simulated resistance. Disadvantages: poor dynamic adjustment capability, large system volume, and inconvenience for digitization and intelligentization.

[0007] Magnetic resistance: the conductor moves in the magnetic field to generate eddy currents to simulate resistance. Disadvantages: poor dynamic adjustment capability, electromagnets need external power supply, and permanent magnets are difficult to obtain.

[0008] Brushless motor resistance: use brushless motor / generator to simulate resistance. Disadvantages: brushless motor control calculation is large, hardware is complex. Motor cost is high, system cost is high. Use FOC algorithm commutation, individual differences of motor will cause algorithm parameters to be fine-tuned, calibration cost is high, parameter deviation will cause output to be unstable, use feeling is poor. Some use diode rectification, diode current is large, there is pressure difference, power is large, it is easy to explode.

[0009] Therefore, a dynamic adjustment and low-cost resistance adjustment method is needed. SUMMARY

[0010] To solve the above-mentioned prior art problems, the present application provides a brush motor resistance control circuit, comprising:

[0011] Control switch and adjustable load;

[0012] Wherein, the control switch receives control signal and controls the on-off of the circuit, the control switch includes first switch, second switch, third switch and fourth switch;

[0013] Wherein, the first switch and the second switch are connected in series, and the third switch and the fourth switch are connected in series;

[0014] The first switch and the second switch have a first connection end between them, and the first connection end is used to connect with one connection electrode of the brush motor;

[0015] The third switch and the fourth switch have a second connection end between them, and the second connection end is used to connect with another connection electrode of the brush motor;

[0016] The first switch and the third switch are connected to one end of the adjustable load away from the first connection end and the second connection end;

[0017] The second switch and the fourth switch are connected to the other end of the adjustable load away from the first connection end and the second connection end;

[0018] Wherein, the two ends of the adjustable load are connected in parallel with a capacitor.

[0019] Further, the adjustable load includes a load and a fifth switch, and the fifth switch and the load are connected in series.

[0020] Further, the first switch, the second switch, the third switch, the fourth switch and the fifth switch are all MOSFET.

[0021] Further, the load is a battery.

[0022] Further, the application also provides a brush motor resistance control method, which controls the brush motor resistance based on the brush motor resistance control circuit, and comprises the following steps:

[0023] S1, performing a resistance dynamic adjustment strategy on the fifth switch, wherein the resistance dynamic adjustment strategy is to control the PWM duty cycle of the fifth switch according to the fitness resistance demand scene;

[0024] S2, controlling the first switch and the fourth switch to be connected at the same time, so that the first switch, the brush motor, the fourth switch and the capacitor are connected to form a first loop;

[0025] S3, disconnecting the first switch and the fourth switch;

[0026] controlling the second switch and the third switch to be connected at the same time, so that the second switch, the brush motor, the third switch and the capacitor are connected to form a second loop;

[0027] S4, alternately controlling the first loop and the second loop to be connected.

[0028] Further, in step S4, the first loop connection time is t1, and the second loop connection time is t2;

[0029] When the first loop and the second loop are alternately controlled to be connected, high-voltage boost control strategy and low-voltage boost control strategy are respectively executed;

[0030] The high-voltage boost control strategy controls t1 to be greater than t2;

[0031] The low-voltage boost control strategy controls t1 to be less than t2.

[0032] Further, the high-voltage boost control strategy and the low-voltage boost control strategy further comprise a time difference adjustment strategy, which adjusts the difference between t1 and t2 according to the boost amplitude demand.

[0033] Further, in step S1, the resistance dynamic adjustment strategy comprises decreasing the PWM duty cycle of the fifth switch when the resistance demand is large, and increasing the PWM duty cycle of the fifth switch when the resistance demand is small.

[0034] Further, it further comprises a constant voltage control strategy, which is to obtain a constant voltage threshold and adjust the voltage in real time according to the constant voltage threshold; the voltage adjustment comprises boost control through the high-voltage boost control strategy or the low-voltage boost control strategy, and step-down control by increasing the PWM duty cycle of the fifth switch.

[0035] Further, in step S1, it further comprises obtaining the current size of the brush motor and calculating the resistance of the brush motor according to the current.

[0036] In step S1, the PWM duty cycle of the fifth switch is feedback adjusted according to the calculated brush motor resistance.

[0037] Further, the application also provides a fitness training device, which adopts the brush motor resistance control method to control the resistance, and is characterized in that:

[0038] The brush DC motor and the control circuit board are included.

[0039] The rotating shaft of the brush motor can be connected with a bicycle transmission.

[0040] The control circuit board is printed with the brush motor resistance control circuit.

[0041] The application has the advantages that the application provides a brush motor resistance control circuit, a control method and a fitness training device, which are used to control the resistance of the brush motor during rotation, and compared with the brushless motor, the brush motor does not need to be separately increased in commutation control, so that the control difficulty of the brush motor is low, the cost of the motor driving circuit is also reduced, and the cost of the brush motor is also lower than that of the brushless motor, the cost of the brush motor is 20% of the cost of the three-phase brushless riding platform motor with similar performance, and the cost proportion of the motor driving circuit is 50% of the cost of the brush motor.

[0042] The resistance of the brush motor can be dynamically adjusted by adjusting the resistance of the brush adjustable load.

[0043] Meanwhile, the voltage in the circuit is also regulated in the application, so that the adjustable range of the resistance of the motor is large, and the fitness equipment is suitable for different scenes. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 The brush motor resistance control circuit provided by the application;

[0045] Figure 2 The first loop schematic diagram provided by the application;

[0046] Figure 3 The second loop schematic diagram provided by the application;

[0047] Figure 4 The structure block diagram of the brush motor resistance control method provided by the application. DETAILED DESCRIPTION

[0048] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0049] Embodiment 1

[0050] With reference to Figure 1 , the embodiment provides a brush motor resistance control circuit, comprising:

[0051] a control switch and an adjustable load;

[0052] The control switch receives a control signal and controls the on-off of the circuit, and the control switch comprises a first switch S1, a second switch S2, a third switch S3 and a fourth switch S4.

[0053] The first switch and the second switch are connected in series, and the third switch and the fourth switch are connected in series.

[0054] The first switch and the second switch have a first connecting end therebetween, and the first connecting end is used to be connected with one connecting electrode of the brush motor M.

[0055] The third switch and the fourth switch have a second connecting end therebetween, and the second connecting end is used to be connected with another connecting electrode of the brush motor M.

[0056] The first switch and the third switch are connected with one end of the adjustable load, which is away from the first connecting end and the second connecting end.

[0057] The second switch and the fourth switch are connected with another end of the adjustable load, which is away from the first connecting end and the second connecting end.

[0058] The two ends of the adjustable load are connected in parallel with a capacitor C.

[0059] In the resistance generation mode of the existing fitness device, there are problems such as poor dynamic adjustment, and the resistance generation mode of the brushless motor which can solve the dynamic adjustment has high cost and high requirement for control.

[0060] The embodiment provides a brush motor resistance control circuit for controlling the resistance of a brush motor, a first connection end and a second connection end connected with two poles of the brush motor are connected with two ends of an adjustable load, when the brush motor is used for movement, the adjustable load connected with the brush motor can consume the power generated by the rotation of the brush motor, and the resistance is generated at the brush motor.

[0061] On this basis, it is known from U=nBSω that U changes with the change of ω, and unstable voltage is generated, which brings complexity to power supply and calculation of other parts of the system.

[0062] Meanwhile, when ω is relatively low, U is relatively low, and when a user needs to perform low-speed high-power fitness, according to P=UI, P is small, and the loop current I is relatively large, which brings challenges to the overcurrent capacity of the system.

[0063] For example, when a bicycle riding platform is used for riding training, a brush motor is used to simulate the resistance of the bicycle when the bicycle is ridden, and in the process of simulating uphill riding, the bicycle is more laborious in the process of uphill riding in actual riding. In order to obtain a more realistic simulation effect, the brush motor needs to provide greater resistance to the bicycle to obtain the simulation effect, and in the process of simulating uphill riding, the current in the loop increases due to the reduction of the rotation speed of the motor, which brings pressure to the circuit of the bicycle riding training platform, and even burns the circuit.

[0064] In the self-generating system, too small U will cause the power supply voltage of the whole system (when the adjustable load is output as power to other components) to be insufficient to work.

[0065] In the embodiment, the output circuit of the motor is controlled through the first switch, the second switch, the third switch and the fourth switch, when the circuit of the brush motor is controlled through the control switches, the first switch and the fourth switch are simultaneously connected, the first switch, the brush motor, the fourth switch and the capacitor are connected to form a first loop, or the second switch and the third switch are simultaneously connected, the second switch, the brush motor, the third switch and the capacitor are connected to form a second loop.

[0066] When the first loop or the second loop is formed, the two poles of the motor are always connected to the circuit through the first connection end and the second connection end respectively.

[0067] The control circuit is connected with the brush motor, and the coil is wound in the brush motor, so that the motor is always in the same loop with the capacitor in the first loop and the second loop, and at this time, the coil in the brush motor is used as an inductor, and the capacitor and the control switch form a boost circuit. By controlling the communication of the first loop and the second loop respectively, the voltage in the brush motor resistance control circuit is raised by using the boost circuit, and the current pressure on the circuit is reduced, so that the brush motor connected with the adjustable load can meet the low-speed high-power fitness demand of the fitness user.

[0068] Embodiment 2:

[0069] Further, the adjustable load comprises a load RL and a fifth switch S5, and the fifth switch and the load are connected in series.

[0070] The load and the fifth switch are connected in series, and the communication time between the load and the circuit can be adjusted by adjusting the duty cycle of the fifth switch, so as to adjust the adjustable load composed of the fifth switch and the load. The load can be selected in other electric appliances or storage batteries, and the electricity generated by the brush motor is utilized.

[0071] Embodiment 3:

[0072] Further, the first switch, the second switch, the third switch, the fourth switch and the fifth switch are MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor).

[0073] The MOSFET has small volume and is convenient to control, so as to quickly switch the loop of the circuit.

[0074] Embodiment 4:

[0075] Reference Figure 4 Further, the application further provides a brush motor resistance control method, which controls the resistance of the brush motor based on the above brush motor resistance control circuit, and comprises the following steps:

[0076] S1, performing a resistance dynamic adjustment strategy on the fifth switch, and the resistance dynamic adjustment strategy is to control the PWM duty cycle of the fifth switch according to the fitness resistance demand scene.

[0077] The PWM duty cycle of the fifth switch is adjusted, that is, the resistance of the adjustable load is adjusted, so as to control the resistance of the brush motor. The PWM duty cycle of the fifth switch is different, so that the brush motor has different resistances, and is suitable for various fitness scenes.

[0078] The resistance dynamic adjustment strategy comprises decreasing the PWM duty cycle of the fifth switch when the resistance demand is large, and increasing the PWM duty cycle of the fifth switch when the resistance demand is small, so as to realize dynamic adjustment of the resistance of the brush motor.

[0079] S2, the first switch and the fourth switch are controlled to be connected at the same time, the first switch, the brush motor, the fourth switch and the capacitor are connected to form a first loop;

[0080] S3, the first switch and the fourth switch are disconnected;

[0081] The second switch and the third switch are controlled to be connected at the same time, the second switch, the brush motor, the third switch and the capacitor are connected to form a second loop;

[0082] S4, the first loop and the second loop are alternately controlled to be connected.

[0083] As can be seen from U=nBSω, U changes with ω, and unstable voltage is generated, which brings complexity to the power supply and calculation of other parts of the system. For example, the circuit for supplying power to the control system processor needs to adapt to a very wide range of power supply voltages.

[0084] At the same time, when ω is relatively low, U will be relatively low. When the user needs to exercise at low speed and high power, according to P=UI, P is large and U is small, the loop current I will be relatively large, which brings challenges to the overcurrent capacity of the system.

[0085] In the embodiment, the output circuit of the motor is controlled through the first switch, the second switch, the third switch and the fourth switch. When the circuit of the brush motor is controlled through these control switches, the first switch and the fourth switch can be controlled to be connected at the same time, the first switch, the brush motor, the fourth switch and the capacitor are connected to form a first loop, or the second switch and the third switch are controlled to be connected at the same time, the second switch, the brush motor, the third switch and the capacitor are connected to form a second loop.

[0086] When the first loop or the second loop is formed, the two poles of the motor are always connected to the circuit through the first connection end and the second connection end respectively.

[0087] After the control circuit is connected to the brush motor, the coil is wound in the brush motor. The motor is always in the same loop with the capacitor in the first loop and the second loop. At this time, the coil in the brush motor is used as an inductor, and the capacitor and the control switch together form a boost circuit. By controlling the first loop and the second loop to be connected respectively, the boost circuit is used to increase the voltage in the brush motor resistance control circuit, reduce the current pressure on the circuit, and make the brush motor connected to the adjustable load as a resistance generation method meet the low-speed high-power fitness needs of fitness users.

[0088] Specifically, as shown in Figure 2 firstly, the first loop is connected, the motor generates electricity to charge the capacitor to obtain a voltage Uc0, and then switched to the second loop, as shown in Figure 3 the stored energy and voltage Uc0 on the capacitor, at this time the loop electromotive force is Uc0+U, the impedance is the MOS on-resistance, the motor internal resistance, and the capacitor ESR, all of which are relatively small, at this time the loop current will increase, and the energy will be stored in the brush motor coil. Then switch to the first loop connection again, because the current of the motor coil inductance is not abrupt, the motor will charge the capacitor with a larger current than the first time. The capacitor voltage Uc1>Uc0. Uc1 can be up to Uc0+U, which can be repeated accumulation, so that the voltage across the capacitor is much higher than that without control.

[0089] Embodiment 5:

[0090] Further, in step S4, the first loop connection time is t1, and the second loop connection time is t2;

[0091] Alternately controlling the first loop and the second loop to be connected respectively performs high-voltage boost control strategy and low-voltage boost control strategy;

[0092] The high-voltage boost control strategy controls t1 to be greater than t2;

[0093] The low-voltage boost control strategy controls t1 to be less than t2.

[0094] By controlling the relative time size of t1 and t2, the boost size of the boost circuit can be adjusted to obtain different voltages in the circuit.

[0095] Embodiment 6:

[0096] Further, the high-voltage boost control strategy and the low-voltage boost control strategy further include a time difference adjustment strategy, which adjusts the difference between t1 and t2 according to the boost amplitude requirement.

[0097] Adjusting the difference between t1 and t2 adjusts the voltage amplitude raised in the boost circuit in one circuit switching period.

[0098] Embodiment 7

[0099] Further, it further includes a constant voltage control strategy, which obtains a constant voltage threshold and adjusts the voltage in real time according to the constant voltage threshold.

[0100] Adjusting the voltage includes boost control through high-voltage boost control strategy or low-voltage boost control strategy, and step-down control by increasing the PWM duty cycle of the fifth switch.

[0101] By the control of the voltage in the circuit, the resistance of the brush motor can be kept constant, and when the resistance of the brush motor is adjusted, the constant resistance can be obtained by adjusting the constant voltage threshold.

[0102] When the external power equipment needs to be powered, the voltage in the circuit is kept stable, and the external power equipment can be continuously powered.

[0103] Embodiment 8:

[0104] Further, in step S1, the current of the brush motor is also acquired, and the resistance of the brush motor is calculated according to the current;

[0105] In step S1, the PWM duty cycle of the fifth switch is feedback adjusted according to the calculated resistance of the brush motor.

[0106] By the feedback adjustment, more accurate resistance adjustment effect can be obtained, and the difference between the expected resistance and the actual resistance after adjustment is avoided.

[0107] Embodiment 9:

[0108] Further, the application also provides a fitness training device, which adopts the brush motor resistance control method to control the resistance, and has the characteristics that:

[0109] The fitness training device comprises a brush DC motor and a control circuit board.

[0110] The control circuit board is printed with the brush motor resistance control circuit.

[0111] In the application, the fitness training device can be a bicycle riding platform, a rowing machine, a power station elliptical machine or a treadmill.

[0112] The brush DC motor is used as the resistance source, and when the fitness training device is used for training, the resistance of the brush DC motor can be dynamically controlled to simulate different fitness scenes in the device, such as uphill, downhill and uphill and downhill alternation in the bicycle riding platform, so that the user can have a more real riding experience.

[0113] Compared with the brushless motor, the fitness training device has a low overall cost, and the logistics cost of the fitness training device with the brush motor is also relatively reduced due to the light weight of the brush motor.

[0114] In the description of the embodiments of the present application, it needs to be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "center", "top", "bottom", "top", "bottom", "inner", "outer", "inner side", "outer side" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. Among them, "inside" refers to the inside or enclosed area or space. "Periphery" refers to the area around a particular component or a particular area.

[0115] In the description of the embodiments of the present application, the terms "first", "second", "third", "fourth" are only used for description purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second", "third", "fourth" can be explicitly or implicitly included one or more. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0116] In the description of the embodiments of the present application, it needs to be explained that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "assembling" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0117] In the description of the embodiments of the present application, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0118] In the description of the embodiments of the present application, it needs to be understood that "-" and "~" represent the range of the same of two numerical values, and the range includes the end points. For example: "A-B" represents a range greater than or equal to A and less than or equal to B. "A~B" represents a range greater than or equal to A and less than or equal to B.

[0119] In the description of the embodiments of the present application, the term "and / or" herein is only a description of the association relationship between the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " herein generally represents that the front and rear associated objects have an "or" relationship.

[0120] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A brushed motor resistance control circuit, characterized in that, include: Control switches and adjustable loads; The control switch receives control signals and controls the circuit to open and close. The control switch includes a first switch, a second switch, a third switch, and a fourth switch. The first and second switches are connected in series, and the third and fourth switches are connected in series. A first connection terminal is provided between the first and second switches, and this first connection terminal is used to connect to one connection electrode of the brushed motor. A second connection terminal is provided between the third and fourth switches, and this second connection terminal is used to connect to another connection electrode of the brushed motor. The ends of the first and third switches furthest from the first and second connection terminals are connected to one end of the adjustable load. The ends of the second and fourth switches furthest from the first and second connection terminals are connected to the other end of the adjustable load. A capacitor is connected in parallel across the two ends of the adjustable load. Specifically, the first switch and the fourth switch can be connected simultaneously to form a first loop by connecting the first switch, the brushed motor, the fourth switch, and the capacitor; or the second switch and the third switch can be connected simultaneously to form a second loop by connecting the second switch, the brushed motor, the third switch, and the capacitor. By controlling the connection of the first loop and the second loop respectively, the voltage in the brushed motor resistance control circuit is increased.

2. The brushed motor resistance control circuit according to claim 1, characterized in that: The adjustable load includes a load and a fifth switch, wherein the fifth switch and the load are connected in series.

3. The brushed motor resistance control circuit according to claim 2, characterized in that: The first switch, the second switch, the third switch, the fourth switch, and the fifth switch are all MOSFETs.

4. A brushed motor resistance control method, wherein the resistance of the brushed motor is controlled based on the brushed motor resistance control circuit according to any one of claims 1-3, characterized in that: Includes the following steps: The first switch and the fourth switch are simultaneously connected, so that the first switch, the brushed motor, the fourth switch and the capacitor are connected to form a first loop. Disconnect the first switch and the fourth switch; Control the second switch and the third switch to be connected simultaneously, so that the second switch, the brushed motor, the third switch and the capacitor are connected to form a second loop; The first loop and the second loop are connected alternately.

5. The brushed motor resistance control method according to claim 4, characterized in that: The connection time of the first loop is t1, and the connection time of the second loop is t2; When the first loop and the second loop are alternately connected, the high-voltage boost control strategy and the low-voltage boost control strategy are executed respectively. The high-voltage boost control strategy controls t1 to be greater than t2; The low-voltage boost control strategy controls t1 to be less than t2.

6. The brushed motor resistance control method according to claim 5, characterized in that: The high-voltage boost control strategy and the low-voltage boost control strategy also include a time difference adjustment strategy, which adjusts the difference between t1 and t2 according to the boost amplitude requirement.

7. The brushed motor resistance control method according to claim 5, characterized in that, The adjustable load includes a load and a fifth switch, wherein the fifth switch and the load are connected in series. It also includes a constant voltage control strategy, which involves obtaining a constant voltage threshold and adjusting the voltage in real time based on the constant voltage threshold. The voltage adjustment includes boost control through a high voltage boost control strategy or a low voltage boost control strategy, and buck control by increasing the PWM duty cycle of the fifth switch.

8. The brushed motor resistance control method according to claim 4, characterized in that, The adjustable load includes a load and a fifth switch, wherein the fifth switch and the load are connected in series, and the method further includes: A dynamic resistance adjustment strategy is implemented for the fifth switch; The dynamic resistance adjustment strategy involves controlling the PWM duty cycle of the fifth switch according to the fitness resistance demand scenario, including reducing the PWM duty cycle of the fifth switch when the resistance demand is high and increasing the PWM duty cycle of the fifth switch when the resistance demand is low.

9. The brushed motor resistance control method according to claim 8, characterized in that: The step of controlling the PWM duty cycle of the fifth switch according to the fitness resistance demand scenario also includes obtaining the current of the brushed motor and calculating the resistance of the brushed motor based on the current. In the step of controlling the PWM duty cycle of the fifth switch according to the fitness resistance demand scenario, the PWM duty cycle of the fifth switch is also adjusted based on the calculated brushed motor resistance.

10. A fitness training device, employing the brushed motor resistance control method according to any one of claims 5-9 for resistance control, characterized in that: Includes brushed DC motors and control circuit boards; The control circuit board is printed with the brushed motor resistance control circuit according to any one of claims 1-4.

Images