Wheelchair and control method thereof

Abstract

The application discloses a wheelchair and a control method thereof, and belongs to the technical field of wheelchair control, which comprises the following steps: a mathematical model of a direct current motor is established by adopting a cross compensation algorithm; a current compensation value of a first motor and a current compensation value of a second motor are calculated; a speed compensation value of the first motor and a speed compensation value of the second motor are calculated; a final speed reference value of the first motor and a final speed reference value of the second motor are calculated; the current compensation value of the first motor is compensated into the armature voltage of the first motor, and the current compensation value of the second motor is compensated into the armature voltage of the second motor; the actual rotating speed of the first motor is controlled to follow the final speed reference value of the first motor, and the actual rotating speed of the second motor is controlled to follow the final speed reference value of the second motor, so that the turning control in the power-assisted driving process is realized. The application can realize smooth and flexible power-assisted turning, and improves the use comfort and safety of the wheelchair.

Description

Technical Field

[0001] This invention relates to the field of wheelchair control technology, and in particular to a wheelchair and a control method thereof. Background Technology

[0002] With the accelerating aging of the population, the increasing number of people with accidental disabilities, and the growing public demand for convenient travel, electric wheelchairs have become an important tool for daily travel for people with mobility impairments (such as those with limb disabilities and the elderly). How to lower the operational barriers of electric wheelchairs, improve the assistive convenience for caregivers, and ensure stability and safety during use has become an urgent issue to be addressed in the current development of electric wheelchair technology. Currently, electric wheelchairs on the market have obvious technical limitations: On the one hand, traditional manual wheelchairs rely entirely on manual pushing, which not only fails to meet the independent use needs of patients with weak muscle control and poor limb coordination, as well as the elderly who are not good at operating machinery, but also places a heavy burden on caregivers. For example, when going uphill, it is necessary to overcome the overall weight of the wheelchair and the user, making it difficult to push; when going downhill, it is necessary to continuously apply a counterforce to control the speed, making it difficult to stop and easily causing accidents such as tipping and sliding; long-term manual operation can also lead to muscle strain in the back and arms of caregivers. To address these issues, the industry has gradually developed electric wheelchairs with power assist functions. These wheelchairs feature an added power assist module that enables automatic pushing and braking, reducing the workload for caregivers. However, existing power assist technologies still have key drawbacks: early power assist solutions mostly used rear-mounted buttons, which only provided unidirectional assistance (such as forward or backward movement only), making them unsuitable for turning scenarios; when turning, the left and right drive motors maintained the same speed and operated in one direction, requiring manual steering to overcome the positive driving force output by the motors, resulting in increased steering resistance, deviation from the turning trajectory, and severe speed fluctuations, seriously affecting user comfort and safety. Summary of the Invention

[0003] To address the aforementioned issues, this invention provides a wheelchair and its control method. A cross-compensation algorithm is used to establish a mathematical model of the DC motor. In power-assisted mode, when the wheelchair is manually turned, the load difference between the two motors is automatically detected, and a differential control signal is generated, ensuring that the outer wheel's rotational speed is greater than the inner wheel's. This achieves smooth and gentle power-assisted turning, significantly reducing manual steering resistance and improving user experience and safety.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: A method for controlling a wheelchair, comprising, A mathematical model of a DC motor is established using a cross-compensation algorithm; Calculate the current compensation value of the first motor and the current compensation value of the second motor; Calculate the speed compensation values ​​of the first motor and the second motor based on the current compensation values ​​of the first motor and the second motor. The final speed reference values ​​of the first motor and the second motor are calculated based on the speed compensation values ​​of the first motor and the second motor. The current compensation value of the first motor is compensated into the armature voltage of the first motor, and the current compensation value of the second motor is compensated into the armature voltage of the second motor. The actual speed of the first motor is controlled to follow the final speed reference value of the first motor, and the actual speed of the second motor is controlled to follow the final speed reference value of the second motor, thereby realizing cornering control during assisted driving.

[0005] More specifically, the mathematical model of a DC motor is expressed as follows: Where V1 is the armature voltage of the first motor, I2 is the current flowing through the armature of the second motor, E1 is the back electromotive force of the first motor, V2 is the armature voltage of the second motor, I1 is the current flowing through the armature of the first motor, E2 is the back electromotive force of the second motor, and R is the total resistance of the armature circuit.

[0006] More specifically, the formula for calculating the current compensation value COMP1 of the first motor is as follows: Where I2 is the current flowing through the armature of the second motor, R1_comp is the resistance compensation coefficient of the first motor, and A_comp is the assist compensation coefficient.

[0007] More specifically, the formula for calculating the current compensation value COMP2 of the second motor is as follows: Where I1 is the current flowing through the armature of the first motor, R2_comp is the resistance compensation coefficient of the second motor, and A_comp is the assist compensation coefficient.

[0008] More specifically, the formula for calculating the speed compensation value M1_ref_comp of the first motor is as follows: Where K1_comp is the speed compensation coefficient of the first motor.

[0009] More specifically, the formula for calculating the speed compensation value M2_ref_comp of the second motor is as follows: Wherein, K2_comp is the speed compensation coefficient of the second motor.

[0010] More specifically, the formula for calculating the final speed reference value M1_ref_new of the first motor is as follows: , Where M1_ref_original is the original speed reference value of the first motor.

[0011] More specifically, the formula for calculating the final speed reference value M2_ref_new of the second motor is as follows: , Where M2_ref_original is the original speed reference value of the second motor.

[0012] More specifically, the current compensation value of the first motor is compensated into the armature voltage of the first motor, that is, the current compensation value COMP1 of the first motor is compensated into I2 in the formula V1= I2R + E1; the current compensation value of the second motor is compensated into the armature voltage of the second motor, that is, the current compensation value COMP2 of the second motor is compensated into I1 in the formula V2= I1R + E2.

[0013] The present invention also provides a wheelchair, which applies the above-mentioned wheelchair control method, including a first motor, a second motor, a first wheel, a second wheel and a control module, wherein the first motor is connected to the first wheel, the second motor is connected to the second wheel, and the control module is connected to the first motor and the second motor.

[0014] Beneficial effects: The wheelchair and its control method of the present invention can achieve a rotational speed of the outer wheel greater than that of the inner wheel when turning, thereby reducing steering resistance, avoiding deviation of the turning trajectory and violent speed fluctuations, thus achieving smooth and gentle assisted turning, and improving the comfort and safety of wheelchair use.

[0015] To make the above-mentioned features and advantages of the invention more apparent and understandable, specific embodiments are described below, and detailed descriptions are provided in conjunction with the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a flowchart of a wheelchair control method according to the present invention.

[0017] Figure 2 This is a schematic diagram of the structure of a wheelchair according to the present invention. Detailed Implementation

[0018] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] like Figure 1 As shown, the present invention provides a wheelchair control method, which includes performing steps S1 to S5 when the wheelchair is in assisted turning.

[0020] Step S1: Establish a mathematical model of the DC motor using a cross-compensation algorithm.

[0021] Step S2: Calculate the current compensation value of the first motor and the current compensation value of the second motor.

[0022] Step S3: Calculate the speed compensation values ​​of the first motor and the second motor based on the current compensation values ​​of the first motor and the second motor.

[0023] Step S4: Calculate the final speed reference value of the first motor and the final speed reference value of the second motor based on the speed compensation value of the first motor and the speed compensation value of the second motor.

[0024] Step S5: The current compensation value of the first motor is compensated into the armature voltage of the first motor, and the current compensation value of the second motor is compensated into the armature voltage of the second motor. The actual speed of the first motor is controlled to follow the final speed reference value of the first motor, and the actual speed of the second motor is controlled to follow the final speed reference value of the second motor, so as to realize the turning control during the assisted driving process.

[0025] More specifically, the first motor controls the first wheel of the wheelchair, and the second motor controls the second wheel of the wheelchair.

[0026] In one specific embodiment, the first wheel is the left wheel of the wheelchair, and the second wheel is the right wheel of the wheelchair.

[0027] In another specific embodiment, the second wheel is the left wheel of the wheelchair, and the first wheel is the right wheel of the wheelchair.

[0028] Furthermore, in step S1, the mathematical model of the DC motor is expressed as follows: Where V1 is the armature voltage of the first motor, I2 is the current flowing through the armature of the second motor, E1 is the back electromotive force of the first motor, V2 is the armature voltage of the second motor, I1 is the current flowing through the armature of the first motor, E2 is the back electromotive force of the second motor, and R is the total resistance of the armature circuit.

[0029] Furthermore, in step S2, the formula for calculating the current compensation value COMP1 of the first motor is as follows: Where I2 is the current flowing through the armature of the second motor, R1_comp is the resistance compensation coefficient of the first motor, and A_comp is the assist compensation coefficient.

[0030] Furthermore, in step S2, the formula for calculating the current compensation value COMP2 of the second motor is as follows: Where I1 is the current flowing through the armature of the first motor, R2_comp is the resistance compensation coefficient of the second motor, and A_comp is the assist compensation coefficient.

[0031] Furthermore, in step S3, the calculation formula for the speed compensation value M1_ref_comp of the first motor is as follows: Where K1_comp is the speed compensation coefficient of the first motor.

[0032] Furthermore, in step S3, the calculation formula for the speed compensation value M2_ref_comp of the second motor is as follows: Wherein, K2_comp is the speed compensation coefficient of the second motor.

[0033] Furthermore, in step S4, the formula for calculating the final speed reference value M1_ref_new of the first motor is as follows: , Where M1_ref_original is the original speed reference value of the first motor.

[0034] Furthermore, in step S4, the formula for calculating the final speed reference value M2_ref_new of the second motor is as follows: , Where M2_ref_original is the original speed reference value of the second motor.

[0035] Further, in step S5, the current compensation value of the first motor is compensated into the armature voltage of the first motor, that is, the current compensation value COMP1 of the first motor is compensated into I2 in the formula V1 = I2R + E1; the current compensation value of the second motor is compensated into the armature voltage of the second motor, that is, the current compensation value COMP2 of the second motor is compensated into I1 in the formula V2 = I1R + E2.

[0036] Furthermore, during assisted turning, the load difference between the inner and outer wheels of the wheelchair is significant. Assuming the left wheel is the inner wheel, controlled by the first motor, and the right wheel is the outer wheel, controlled by the second motor, the inner wheel experiences a larger load, meaning a larger current I1 flows through the armature of the first motor; the outer wheel experiences a smaller load, meaning a smaller current I2 flows through the armature of the second motor. In this scenario, the current compensation value COMP1 of the first motor is calculated based on the armature current I2 of the second motor, and its value is relatively small. After compensating the first motor's current compensation value COMP1 to I2 in the formula V1 = I2R + E1, the resulting armature voltage V1 of the first motor is also relatively small, and the final speed reference value M1_ref_new of the first motor is also relatively small. Conversely, the current compensation value COMP2 of the second motor is calculated based on the armature current I1 of the first motor, and its value is relatively large. After compensating the second motor's current compensation value COMP2 to I1 in the formula V2 = I1R + E2, the resulting armature voltage V2 of the second motor is also relatively large, and the final speed reference value M2_ref_new of the second motor is also relatively large. Consequently, the target speed of the outer wheel, i.e., the final speed reference value M2_ref_new of the second motor, is greater than the target speed of the inner wheel, i.e., the final speed reference value M1_ref_new of the first motor. By adjusting the duty cycle of the PWM signal of the outer wheel motor to be greater than that of the PWM signal of the inner wheel motor, a differential control signal is generated, making the armature voltage of the outer wheel motor greater than that of the inner wheel motor, thereby making the speed of the outer wheel greater than that of the inner wheel, ultimately achieving a smooth and responsive power steering.

[0037] More specifically, the resistance compensation coefficient R1_comp of the first motor and the resistance compensation coefficient R2_comp of the second motor are related to the internal resistance of the motor.

[0038] Optionally, the resistance compensation coefficient R1_comp of the first motor can be 70% of the internal resistance value of the first motor. Optionally, the resistance compensation coefficient R2_comp of the second motor can be 70% of the internal resistance value of the second motor.

[0039] More specifically, the assist compensation coefficient A_comp is related to the motor type. The assist compensation coefficient A_comp is used to reduce the impact of cross compensation and prevent overcompensation from causing the motor to overshoot and causing discomfort to the human body.

[0040] Optionally, the value of the assist compensation coefficient A_comp ranges from 0 to 1. The smaller the value of the assist compensation coefficient A_comp, the more the impact of cross compensation can be reduced.

[0041] More specifically, the speed compensation coefficients K1_comp of the first motor and K2_comp of the second motor are used to unify the per-unit values ​​of the current compensation values ​​COMP1 of the first motor and COMP2 of the second motor with the per-unit values ​​of the original speed reference values ​​M1_ref_original of the first motor and M2_ref_original of the second motor, so that the speed compensation values ​​are correctly added to the original speed reference values.

[0042] Optionally, the speed compensation coefficient K1_comp of the first motor and the speed compensation coefficient K2_comp of the second motor are in the range of 1.0-3.0.

[0043] More specifically, when the motor load increases (i.e., the current flowing through the motor armature increases), the motor winding voltage increases, which will lead to a decrease in effective voltage and a decrease in motor speed. The current compensation value is used to offset this voltage drop caused by the motor winding. At a given speed, the duty cycle is increased to offset this partial voltage drop, so that the actual speed is close to the final speed reference value.

[0044] Furthermore, the wheelchair control method of the present invention also includes, when the wheelchair is in normal operation, using a joystick to control the speed difference between the two wheels of the wheelchair when turning, so as to achieve the purpose of smooth turning.

[0045] like Figure 2 As shown, the present invention also provides a wheelchair, which uses the above-mentioned wheelchair control method, including a first motor 1, a second motor 2, a first wheel 3, a second wheel 4 and a control module 5. The first motor 1 is connected to the first wheel 3, the second motor 2 is connected to the second wheel 4, and the control module 5 is connected to the first motor 1 and the second motor 2.

[0046] More specifically, the first motor 1 receives the control signal output by the control module 5 and controls the first wheel 3; the second motor 2 receives the control signal output by the control module 5 and controls the second wheel 4. The control module 5 uses the above-mentioned wheelchair control method for control.

[0047] In summary, this invention provides a wheelchair and its control method, applicable to dual-motor coupling scenarios (such as differential steering wheelchairs). During power assistance, cross-compensation control is activated to prevent the inconvenience of turning caused by unidirectional power assistance. During power assistance, the direction is singular, and the left and right wheels move at the same speed. When turning, the wheelchair's direction can only be manually changed, which is prone to resistance and unstable turning speed. In this invention, the inner and outer wheels experience different external forces during turning, resulting in different currents in the armatures of the corresponding motors. The currents flowing through the two motor armatures are substituted into the motor's mathematical model to calculate the current compensation values ​​for the two motors. These compensation values ​​are then used to calculate the armature voltage and adjust the final speed reference value, ensuring that the outer wheel rotates faster than the inner wheel during turning. This reduces steering resistance, avoids deviation from the turning trajectory and severe speed fluctuations, thereby achieving smooth and gentle power-assisted turning and improving the comfort and safety of the wheelchair.

[0048] It should be understood that although the steps in the flowcharts of the accompanying drawings are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some of the steps in the accompanying drawings may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0049] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for controlling a wheelchair, characterized in that, include, A mathematical model of the DC motor is established using a cross-compensation algorithm. The expression of the mathematical model is as follows: in, The armature voltage of the first motor. The current flowing through the armature of the second motor. The back electromotive force of the first motor is... This is the armature voltage of the second motor. The current flowing through the armature of the first motor. R is the back electromotive force of the second motor, and R is the total resistance of the armature circuit. The current compensation values ​​for the first motor and the second motor are calculated using the following formulas: in, The current flowing through the armature of the first motor. The current flowing through the armature of the second motor. This is the resistance compensation coefficient for the first motor. This is the resistance compensation coefficient for the second motor. To assist in the compensation coefficient; Calculate the speed compensation values ​​of the first motor and the second motor based on the current compensation values ​​of the first motor and the second motor. The final speed reference values ​​of the first motor and the second motor are calculated based on the speed compensation values ​​of the first motor and the second motor. The current compensation value of the first motor is added to the armature voltage of the first motor, that is, the current compensation value of the first motor... Compensation to In In the middle; the current compensation value of the second motor is added to the armature voltage of the second motor, controlling the actual speed of the first motor to follow the final speed reference value of the first motor, that is, the current compensation value of the second motor. Compensation to In In the middle; the actual speed of the second motor is controlled to follow the final speed reference value of the second motor, so as to realize the turning control during the assisted driving process.

2. The wheelchair control method as described in claim 1, characterized in that, Speed ​​compensation value of the first motor The calculation formula is as follows: in, This is the speed compensation coefficient for the first motor.

3. The wheelchair control method as described in claim 1, characterized in that, Speed ​​compensation value of the second motor The calculation formula is as follows: in, This is the speed compensation coefficient for the second motor.

4. The wheelchair control method as described in claim 1, characterized in that, Reference value of the final speed of the first motor The calculation formula is as follows: ， in, This is the original speed reference value for the first motor.

5. The wheelchair control method as described in claim 1, characterized in that, Reference value of the final speed of the second motor The calculation formula is as follows: ， in, This is the original speed reference value for the second motor.

6. A wheelchair, characterized in that, The wheelchair control method according to any one of claims 1-5 includes a first motor, a second motor, a first wheel, a second wheel, and a control module, wherein the first motor is connected to the first wheel, the second motor is connected to the second wheel, and the control module is connected to the first motor and the second motor.

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