Electric waist support with limit protection function and office chair

Abstract

An electric lumbar support with limit protection function includes a controller. The controller performs limit control on the drive motor according to the following steps: Step S1: Obtain the real-time current value of the drive motor. When the real-time current value exceeds a preset current threshold, step S2 is initiated; Step S2: Obtain the current position of the lumbar support body and compare the current position with a preset stroke end position. If the current position is within the allowable deviation range of the stroke end position, the current state is determined to be the stroke end position. Otherwise, step S3 is executed; Step S3: Calculate the current change rate. If the current change rate is greater than a first change rate threshold, the current state is determined to be a foreign object jamming, and the controller controls the drive motor to perform a retraction action. If the current change rate is less than a second change rate threshold, the current state is determined to be an obstructed load. This invention avoids the crude control of the prior art that uniformly executes stop or retraction for different resistances without increasing hardware costs.

Description

Technical Field

[0001] This invention relates to the field of seating technology, and more specifically to an electric lumbar support with a limit protection function. Background Technology

[0002] Electric lumbar support has become an important comfort feature in modern seats. It uses a drive motor to move the lumbar support body forward and backward, providing adjustable support to the user's lower back. To enhance the user experience, electric lumbar support typically features a one-touch adjustment function, allowing users to move the lumbar support to the desired position using control buttons.

[0003] In the control process of electric lumbar supports, limit protection is a key technical aspect to ensure the reliability and safety of the system. In existing technologies, some electric lumbar supports employ mechanical limit structures, which involve setting a physical stop at the end of the travel stroke. When the lumbar support reaches the end point, the mechanical block forces the motor to stop. However, this method can cause the motor to stall, generating significant impact and noise, and long-term use can easily lead to wear and even breakage of the transmission mechanism.

[0004] Other existing technologies achieve protective control by monitoring the current of the drive motor. For example, Chinese patent CN114590184B proposes a method for controlling the lumbar support of a vehicle seat, which determines whether the lumbar support is in the most comfortable position by detecting whether the actual current of the drive motor is greater than a comfort threshold. If the actual current is greater than the comfort threshold, the drive motor stops outputting torque. However, the above-mentioned existing technologies still have the following problems and drawbacks:

[0005] First, in actual use cases, "increased current" may come from three completely different situations: the lumbar support reaches the end of its mechanical stroke, a foreign object is stuck in the transmission mechanism, or the user's back applies additional pressure to the lumbar support. However, existing technology cannot distinguish between different types of resistance, and its current signal processing method is singular, uniformly executing a stop or retraction action. Stopping operation during normal pressure application would seriously affect the user experience.

[0006] Second, when the lumbar support encounters a foreign object during operation, existing technologies usually only stop the machine or simply reverse it, requiring manual intervention from the user. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this application is to provide an electric lumbar support with limit protection function, thereby solving at least one of the above-mentioned technical problems.

[0008] An electric lumbar support with limit protection function includes a lumbar support body, a drive motor, a transmission mechanism, a current detection module, a position detection module, and a controller. The controller performs limit control on the drive motor using the following steps:

[0009] Step S1: Obtain the real-time current value of the drive motor through the current detection module. When the real-time current value exceeds the preset current threshold, start the limit judgment process.

[0010] Step S2: Obtain the current position of the lumbar support body through the position detection module, and compare the current position with the preset end point of the travel:

[0011] If the current position is within the allowable deviation range of the end point of the journey, then the current state is determined to be that the end point of the journey has been reached;

[0012] If the current position is not within the allowable deviation range of the end point of the journey, then proceed to step S3;

[0013] Step S3: Calculate the derivative of the real-time current value with respect to time to obtain the rate of change of current, and perform the following operations based on the value of the rate of change of current:

[0014] If the rate of change of current is greater than the first rate of change threshold, the current state is determined to be foreign object jamming, and the controller controls the drive motor to perform a retraction action;

[0015] If the current change rate is less than the second change rate threshold, the current state is determined to be an obstructed load, and the controller controls the drive motor to decelerate and maintain forward direction.

[0016] The above technical solution separates "reaching the end of the journey" from the phenomenon of increased current by checking the position in step S2, and then distinguishes "foreign object jamming (large rate of change)" and "obstructed load (small rate of change)" in terms of physical mechanism by measuring the magnitude of the current change rate in step S3. This avoids the crude control of the existing technology that uniformly executes stop or retraction for different resistances.

[0017] Wherein, the first rate of change threshold is greater than the second rate of change threshold.

[0018] Preferably, the preset current threshold is 1.2 to 1.5 times the rated current of the motor.

[0019] Preferably, the allowable deviation range of the end point of the journey is ±1mm.

[0020] Preferably, the first rate of change threshold is 20 A / s, and the second rate of change threshold is 5 A / s.

[0021] Preferably, the position detection module is a Hall sensor, and in step S2, the current position of the lumbar support body is calculated by detecting the cumulative number of pulses of the drive motor shaft.

[0022] Preferably, the position detection module is a potentiometer or an angle sensor, and in step S2, the current position of the lumbar support body is directly read by detecting the voltage value or angle value.

[0023] Preferably, the retraction action is the controller controlling the drive motor to rotate in the opposite direction for a predetermined distance.

[0024] Preferably, the predetermined travel distance is 5mm.

[0025] Furthermore, after determining in step S3 that a foreign object is stuck and controlling the drive motor to perform a reversing action, the controller also performs the following steps:

[0026] Step S4: Control the drive motor to move forward again at a first retry speed lower than the normal operating speed, and repeat steps S1 to S3, wherein the normal operating speed is the standard forward speed of the drive motor when there is no load and the limit protection is not triggered.

[0027] Furthermore, in step S4, if it is determined again that a foreign object is stuck, the retraction action and the first retry speed forward are repeated, and the number of attempts by the drive motor to perform the first retry speed forward is accumulated; when the number of attempts reaches a preset threshold, the controller controls the drive motor to retract to the initial position and issues a prompt signal.

[0028] Preferably, the preset number of times threshold is 2 times.

[0029] Preferably, the first retry speed is 20% of the normal operating speed.

[0030] Preferably, in step S4, when the controller controls the drive motor to move forward again at the first retry speed, it simultaneously monitors the current change trend within a time T1 from the start of the drive motor rotating at the first retry speed, where T1 is less than T0, and T0 represents the time taken for the current value of the motor to reach the current threshold when it moves forward again at the first retry speed; if the real-time current value continues to rise within T1 and the current position does not change, it is directly determined to be an impassable obstacle, step S4 is terminated, and the drive motor is controlled to perform a reversing action.

[0031] The present invention also relates to an office chair that includes the electric lumbar support described in any of the above technical solutions.

[0032] In summary, the present invention has the following beneficial effects:

[0033] 1. In this invention, the "reaching the end of the journey" phenomenon is separated from the current increase phenomenon by the position verification in step S2. Then, by the magnitude of the current change rate in step S3, the "foreign object jamming" and "obstructed load" are distinguished in terms of physical mechanism, thereby avoiding the crude control of the existing technology that uniformly executes stop or retraction for different resistances.

[0034] 2. This invention, through the retry mechanism of retreating and then advancing again at a low speed in step S4, can automatically attempt to resume operation. For minor obstructions (such as soft objects, wire ends, etc.), the fault can be eliminated and normal operation restored without user intervention, reducing the frequency of after-sales maintenance. At the same time, by setting a retry number threshold and a rapid prediction mechanism within T1 after startup, it ensures that when a hard obstacle cannot be passed, the complete attempt can be terminated in advance and the system can retreat to a safe position, reducing the impact on motor life. In addition, this mechanism also plays the role of "rapid hard obstacle assertion", which greatly shortens the subsequent retry time - eliminating the need to go through the entire process of advancing → current triggering → position verification → current change rate calculation → judgment and retreat, significantly improving the system response speed.

[0035] 3: This invention sets a preset threshold of 2 attempts, achieving a good balance between repair success rate and security.

[0036] 4: In step S1 of this invention, the current threshold is set to be greater than the rated current, rather than the rated current value, so that it can be reliably triggered when the load increases significantly, while avoiding false triggering caused by normal load fluctuations. Attached Figure Description

[0037] Figure 1 This is a flowchart of the controller performing limit control on the drive motor in Example 1;

[0038] Figure 2 This is a flowchart of the controller performing limit control on the drive motor in Example 2;

[0039] Figure 3 This is a structural block diagram of an electric lumbar support. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0041] Example 1:

[0042] An electric lumbar support with limit protection function, see Figure 3 As shown, it includes the necessary hardware structure such as the lumbar support body, drive motor, transmission mechanism, current detection module, position detection module, and controller.

[0043] The drive motor is a DC brushed motor or a DC brushless motor. Its output shaft is connected to the lumbar support body through a transmission mechanism, driving the lumbar support body to reciprocate in the front-back direction.

[0044] The current detection module is connected in series with the drive motor to collect the motor's operating current signal in real time. It can be implemented using a sampling resistor in conjunction with an operational amplifier, or it can use a Hall current sensor.

[0045] The position detection module is used to detect the current position of the lumbar support body. It can be a Hall sensor, located at the shaft end of the drive motor, to detect the rotation angle or number of rotations. The controller counts the pulse signals output by the Hall sensor and calculates the current displacement of the lumbar support body based on the transmission ratio and lead of the transmission mechanism corresponding to each rotation of the motor shaft, thus determining the current position. Hall sensors have advantages such as low cost, vibration resistance, and no contact wear. Alternatively, the position detection module can be a potentiometer or an angle sensor. The potentiometer is a linear potentiometer, with its sliding end linked to the output end of the lumbar support body or transmission mechanism. By detecting the output voltage value of the potentiometer, the current position of the lumbar support body can be directly calculated.

[0046] The controller is a microcontroller unit (MCU). Its input terminals are electrically connected to the current detection module and the position detection module, respectively, and its output terminal is electrically connected to the drive circuit of the drive motor to control the start, stop, direction and speed of the motor.

[0047] The above are all existing technologies, and are only briefly introduced.

[0048] The key point is to change the controller's control method without adding hardware. For details, see [link to relevant documentation]. Figure 1 As shown, the controller performs limit control on the drive motor using the following steps:

[0049] Step S1: Obtain the real-time current value of the drive motor through the current detection module. Under normal operating conditions, the motor current is maintained within a certain range. When the lumbar support is subjected to external resistance or reaches the end of the stroke, the load increases and the current rises accordingly. At this time, the controller compares the real-time current value with the preset current threshold. When the real-time current value exceeds the threshold, the limit judgment process is started, i.e., step S2 below.

[0050] The preset current threshold is typically set to 1.2 to 1.5 times the rated current of the motor. In this embodiment, it is set to 1.3 times. Taking a typical small DC motor with a rated current of 0.5 to 0.6A as an example, the current threshold is 0.8A. Setting the current threshold to be greater than the rated current, rather than the rated current value, ensures reliable triggering when the load increases significantly, while avoiding false triggering caused by normal load fluctuations (such as current fluctuations caused by friction changes on the guide rail).

[0051] Step S2: Obtain the current position of the lumbar support body through the position detection module and compare it with the preset stroke end position. The stroke end position corresponds to the maximum allowable movement distance of the lumbar support in the forward direction. It is determined during the product design stage based on the stroke range of the mechanical structure. The allowable deviation range of the stroke end position is set to ±1mm. This deviation range takes into account both the measurement accuracy of the position detection module and the mechanical transmission clearance.

[0052] If the current position is within the allowable deviation range of the end point of the stroke, it means that the lumbar support has approached or reached the physical end point of the mechanical stroke. At this time, the increase in current is a normal phenomenon. The controller determines that the current state has reached the end point of the stroke and controls the drive motor to stop running. If the current position is not within the allowable deviation range of the end point of the stroke, it means that the increase in current is not due to reaching the end point, but an abnormality has occurred during operation. At this time, the controller executes the following step S3.

[0053] Step S3: Operating condition classification and differentiated control based on current change rate. Specifically, the controller calculates the derivative of the real-time current value with respect to time to obtain the current change rate. The current change rate reflects the severity of load changes and is the core criterion for distinguishing different resistance types.

[0054] If the rate of change of current is greater than the first rate of change threshold (in this embodiment, the first rate of change threshold is set to 20A / s, and the specific setting of this value is described later), it indicates that the current rises sharply in a very short time. This characteristic corresponds to the lumbar support suddenly encountering a foreign object (such as lint from the backrest, large dust particles, etc.) and getting stuck during operation. At this time, the controller determines that the foreign object is stuck and controls the drive motor to perform a reversing action, causing the lumbar support to move in the opposite direction for a certain distance, releasing the pressure on the foreign object and preventing damage to the transmission mechanism.

[0055] If the rate of change of current is less than the second rate of change threshold (the second rate of change threshold is less than the first rate of change threshold; the second rate of change threshold is set to 5A / s, and the specific setting of this value is described later), it indicates that the current rise is relatively gradual. This characteristic corresponds to the lumbar support being subjected to flexible pressure from the user's back during operation (human muscles are elastic, and the pressure on the lumbar support gradually increases). At this time, the controller determines it as an obstructed load and controls the drive motor to decelerate while maintaining forward movement. Deceleration can prevent the lumbar support from rapidly pushing against the user's back, causing discomfort, while maintaining the forward direction means that the lumbar support continues to provide support, and the user will not feel a loss of support due to a sudden stop.

[0056] If the current change rate is greater than or equal to the second change rate threshold and less than or equal to the first change rate threshold, the current state is determined to be an uncertain load. The controller controls the drive motor to continue moving forward at the current speed and continuously monitors the real-time current value and the current change rate.

[0057] 20 A / s corresponds to the typical characteristics of jamming. When the lumbar support encounters an obstacle and becomes jammed during operation, the time for the load to suddenly increase from the normal value to the stall value is usually within 10 to 30 ms. If the current change is 0.2 to 0.6 A, the rate of change is approximately 10 to 60 A / s. Taking its typical lower limit of 20 A / s as the first threshold can effectively capture jamming events while avoiding misjudgments caused by signal noise. 5 A / s corresponds to the typical characteristics of flexible pressure applied by the human body. The pressure applied by the user's back to the lumbar support is a muscle exertion process, and the duration of the load increase is usually more than 100 ms. If the current change is 0.2 to 0.6 A, the rate of change is approximately 2 to 6 A / s. Taking its typical upper limit of 5 A / s as the second threshold can ensure that the human body pressure condition is correctly identified as an obstructed load and not misjudged as foreign object jamming. There is a margin of 4 times between the first rate of change threshold of 20A / s and the second rate of change threshold of 5A / s, providing sufficient criterion differentiation space. This allows the controller to handle current change rates between the two (such as 5A / s to 20A / s) according to a preset safety strategy (e.g., maintaining deceleration and continuing monitoring), which has high robustness.

[0058] In this embodiment, the retraction action is achieved by the controller controlling the drive motor to rotate in the opposite direction for a predetermined stroke distance, which is 5mm. When a foreign object is detected as stuck, the controller controls the drive motor to rotate in the opposite direction, causing the lumbar support to retract by 5mm. Verification has shown that a 5mm retraction is sufficient to dislodge common foreign objects stuck inside the transmission mechanism from the meshing gap, releasing compressive stress; simultaneously, this retraction is not excessive, preventing the lumbar support from retracting too much and significantly reducing the effective support stroke.

[0059] It can be seen that the controller, through the position verification in step S2, separates "reaching the end of the journey" from the phenomenon of increased current, and then through the magnitude of the current change rate in step S3, it makes a fundamental distinction between "foreign object jamming" and "obstructed load" in terms of physical mechanism, thereby avoiding the crude control of the existing technology that uniformly executes stop or retraction for different resistances.

[0060] Example 2:

[0061] The difference between this embodiment and Embodiment 1 is that, see... Figure 2 As shown, after determining that a foreign object is stuck and controlling the drive motor to perform a retraction action in step S3, the controller also performs the following steps:

[0062] Step S4: The controller controls the drive motor to move forward again at a first retry speed lower than the normal operating speed, and repeats steps S1 to S3. Here, the normal operating speed is the standard forward speed of the drive motor when there is no load and the limit protection is not triggered.

[0063] The purpose of this step is as follows: Some foreign objects (such as soft fabric fibers, thread ends, and small particles) may adhere to the surface of the transmission mechanism after being squeezed by the lumbar support. Through a single retraction operation, the foreign objects may have been dislodged or their position may have shifted. However, the system needs to verify this result. Probing at a low speed can reduce the impact force before the foreign objects are completely dislodged, thus avoiding secondary damage to the mechanism. If the probe passes (i.e., no abnormality is triggered when the judgment process is re-executed), the lumbar support will resume normal operation. If the probe triggers the foreign object jamming judgment again, it indicates that the foreign object cannot be removed on its own, and the system will perform further processing measures, as detailed below.

[0064] The first test speed is 20% of the normal operating speed. Reducing the speed can significantly reduce the impact kinetic energy (proportional to the square of the speed), greatly reducing the mechanical stress on the system when it comes into contact with an obstacle, while providing the user with sufficient reaction time.

[0065] In step S4, if the obstruction is again determined to be caused by a foreign object, the retraction action and the first retry speed forward are repeated, and the number of attempts by the drive motor to advance at the first retry speed is accumulated. When the number of attempts reaches a preset threshold, the controller controls the drive motor to retract to the initial position and issues a prompt signal. The preset threshold is 2 times.

[0066] Setting a preset threshold of 2 attempts is based on the following considerations: A single revert and retrieval is the most common self-repair attempt, with a high success rate; if the first retry fails, an additional revert and retrieval (cumulatively a second attempt) can resolve jamming caused by a change in the foreign object's position but not yet complete removal—for example, the foreign object shifted during the first revert but became stuck in a different location; if both retries fail, it indicates the foreign object is hard and large enough to be expelled by simple reciprocating motion, and continuing to attempt this will only increase the risk of motor stalling and burnout. In this case, the controller will revert the motor to its initial position and issue a warning signal via an external alert device, such as a voice broadcast device, informing the user that manual inspection is required. The 2-attempt threshold achieves a good balance between repair success rate and safety.

[0067] In a further embodiment, in step S4, when the controller controls the drive motor to move forward again at the first retry speed, it simultaneously monitors the current change trend within a time period T1 (200ms in this embodiment) from the start of the drive motor rotating at the first retry speed. Here, T1 is less than T0, and T0 represents the time taken for the current value of the motor to reach the current threshold when it moves forward again at the first retry speed. If the real-time current value continues to rise within T1 and the current position does not change, it is directly determined to be an impassable obstacle, and step S4 is terminated and the drive motor is controlled to perform a reversing action.

[0068] The reason for setting up this rapid prediction mechanism is that when the foreign object does not fall off after the first retraction, the lumbar support will move forward again at the first retry speed, which is very likely to cause the motor to stall again. If we wait for the current to exceed the threshold before making a judgment according to the conventional procedure, the motor may already be in a stalled state during this period. Although the time is very short, the long-term accumulation will still affect the life of the motor.

[0069] By setting T1 to be less than T0, the pre-judgment is initiated before the current reaches the trigger threshold. By monitoring the combined characteristic of "current continuously rising and position remaining unchanged" within T1 time, the controller can preemptively determine that an obstacle is impassable, terminate the complete attempt in advance, and execute a backoff, keeping the motor stall time within T1 (200ms), reducing the impact on motor lifespan. At the same time, this mechanism also serves as a "fast assertion of hard obstacles," significantly shortening the subsequent retry time—eliminating the need for the entire process of forward movement → current triggering → position verification → current change rate calculation → judgment and backoff, thus significantly improving the system response speed.

[0070] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the concept and scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the design concept of the present invention should fall within the protection scope of the present invention. The technical content for which protection is sought in this invention has been fully described in the claims.

Claims

1. An electric-powered lumbar support with a limit protection function, comprising a lumbar support body, a driving motor, a transmission mechanism, a current detection module, a position detection module and a controller, characterized in that, The controller performs limit control on the drive motor using the following steps: Step S1: Obtain the real-time current value of the drive motor through the current detection module. When the real-time current value exceeds the preset current threshold, start step S2. Step S2: Obtain the current position of the lumbar support body through the position detection module, and compare the current position with the preset end point of the travel: If the current position is within the allowable deviation range of the end point of the travel, then the current state is determined to be the end point of the travel, and the drive motor is controlled to stop running; If the current position is not within the allowable deviation range of the end point of the journey, then proceed to step S3; Step S3: Calculate the derivative of the real-time current value with respect to time to obtain the rate of change of current, and perform the following operations based on the value of the rate of change of current: If the rate of change of current is greater than the first rate of change threshold, the current state is determined to be foreign object jamming, and the controller controls the drive motor to perform a retraction action; If the rate of change of current is less than the second rate of change threshold, the current state is determined to be an obstructed load, and the controller controls the drive motor to decelerate and maintain the forward direction. Wherein, the first rate of change threshold is greater than the second rate of change threshold.

2. The electrically powered lumbar support with a limit protection function according to claim 1, characterized in that, The preset current threshold is 1.2 to 1.5 times the rated current of the motor.

3. The electrically powered lumbar support with a limit protection function according to claim 1, characterized in that, The allowable deviation range for the end point of the journey is ±1mm.

4. The electric lumbar support with limit protection function according to claim 1, characterized in that, The retraction action is achieved by the controller controlling the drive motor to rotate in the opposite direction for a predetermined stroke distance; the predetermined stroke distance is 5mm.

5. The electrically powered lumbar support with a limit protection function according to claim 1, characterized in that, After determining in step S3 that a foreign object is stuck and controlling the drive motor to perform a retraction action, the controller further performs the following steps: Step S4: Control the drive motor to move forward again at a first retry speed lower than the normal operating speed, and repeat steps S1 to S3, wherein the normal operating speed is the standard forward speed of the drive motor when there is no load and the limit protection is not triggered.

6. The electric lumbar support with limit protection function according to claim 5, characterized in that: In step S4, if it is determined again that a foreign object is stuck, the retraction action and the first retry speed forward are repeated, and the number of attempts of the drive motor to perform the first retry speed forward is accumulated. When the number of attempts reaches a preset threshold, the controller controls the drive motor to return to the initial position and issues a prompt signal.

7. The electric lumbar support with limit protection function according to claim 6, characterized in that: The preset threshold number of times is 2.

8. The electric lumbar support with limit protection function according to claim 5, characterized in that: The first retry speed is 20% of the normal operating speed.

9. The electric lumbar support with limit protection function according to claim 5, characterized in that: In step S4, when the controller controls the drive motor to move forward again at the first retry speed, it simultaneously monitors the current change trend within a time T1 from the start of the drive motor rotating at the first retry speed, where T1 is less than T0, and T0 represents the time taken for the current value of the motor to reach the current threshold when it moves forward again at the first retry speed; if the real-time current value continues to rise within T1 and the current position does not change, it is directly determined to be an impassable obstacle, step S4 is terminated, and the drive motor is controlled to perform a reversing action.

10. An office chair comprising the electric lumbar support as described in any one of claims 1 to 9.

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