Ergonomic chair cushion depth adjustment control method

Abstract

The application discloses an ergonomic chair cushion depth adjustment control method, comprising the following steps: collecting the instantaneous subsidence profile of the rear part of the cushion sponge in real time through the zoned deployment of the subsidence depth detection unit, and obtaining the initial subsidence evaluation result by combining the sponge rebound recovery form obtained after unloading with the rebound response detection unit; calculating the horizontal projection shortening length according to the instantaneous subsidence profile and the sponge rebound recovery form, determining the permanent collapse sign of the part with the horizontal projection shortening length exceeding the elastic recovery limit, and obtaining the forward stroke adjustment range accordingly; matching the horizontal projection shortening length with the forward stroke adjustment range, determining the necessary amplitude of the slide rail forward push corresponding to the area where the permanent collapse sign is located as the seat depth adjustment scheme; driving the slide rail to execute the forward push action according to the forward push control signal, synchronously collecting the horizontal projection length and the knee rear side gap state after execution, and obtaining the adjusted subsidence recovery seat depth stability by combining the rebound change.

Description

Technical Field

[0001] This invention relates to the field of information technology, and in particular to a method for adjusting and controlling the depth of an ergonomic chair seat cushion. Background Technology

[0002] The design and optimization of ergonomic chairs is a crucial issue in modern offices and homes, directly impacting user comfort and health. In prolonged sitting, seat depth adjustment is key to alleviating fatigue and protecting leg and lower back health. The seat design of an ergonomic chair not only affects posture but also closely aligns with the user's body shape. Improperly set seat depth can lead to unsupported thighs or pressure on the back of the knees, causing poor blood circulation and increased strain on the lumbar spine over time. Currently, many ergonomic chair seat depth adjustment methods on the market focus only on initial comfort, neglecting the impact of material changes during use on the adjustment strategy.

[0003] In the prior art, a seat cushion and an auxiliary learning chair equipped with the seat cushion, disclosed in CN108634696A, disclose a technology that actively adjusts the surface support shape of the seat cushion and backrest cushion through a pressure sensor, a control module, and a movable support body, and changes the seat depth by adjusting the relative distance between the seat cushion and backrest cushion. This disclosed technology relies solely on pressure data, sitting duration, and changes in the position of the support body to adjust the seat support, failing to distinguish between temporary pressure-induced sinking of the rear of the seat cushion and permanent collapse caused by long-term material aging. This may lead to a deviation of the seat depth compensation from the user's actual thigh support length after long-term use. These methods are typically designed based on simple pressure distribution or fixed parameters, determining a standard adjustment range through testing at the time of manufacture, but they fail to adequately consider the potential performance degradation of the seat cushion material over time.

[0004] In actual use, seat cushion materials gradually lose their resilience due to repeated weight-bearing, and the rate of degradation varies greatly among different materials. Memory foam cushions may show noticeable slow rebound after six months of use, while high-density polyurethane cushions may take more than a year to show performance decline. This neglect means that the adjustment mechanism cannot accurately adapt to the user's actual needs when faced with material aging or deformation, thus affecting the support effect on the sitting posture. The back of the seat cushion is usually the main area bearing the pressure of the buttocks, and its degree of sagging directly affects the actual support length of the thighs. This sagging may be caused by temporary pressure or irreversible collapse of the material after long-term use. If these two sagging states cannot be distinguished, the adjustment mechanism may incorrectly compensate for the seat depth, causing unnecessary adjustment deviations. For example, when a user sits on a chair, the back of the seat cushion temporarily sags due to pressure, and theoretically, the seat cushion should be moved forward to compensate for the lack of thigh support; however, if the material has permanently collapsed due to long-term use, moving the seat cushion forward will actually make the seat depth exceed the actual length of the thighs, causing pressure on the back of the knees and causing discomfort.

[0005] Therefore, how to accurately determine whether the sinking of the rear of the seat is a temporary pressure or a permanent collapse, and dynamically adjust the seat depth accordingly to ensure that the thigh support length always meets the user's actual needs, has become a key problem that this study urgently needs to solve. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an ergonomic chair seat depth adjustment and control method, which solves the problem that if the seat depth is not set properly in the existing technology, the upper thighs will be unsupported or the back of the knees will be squeezed, which will cause poor blood circulation and increased burden on the lumbar spine with long-term use.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for adjusting the depth of an ergonomic chair seat cushion, the method comprising:

[0009] The indentation depth detection unit deployed in a zone collects the instantaneous indentation profile of the sponge at the back of the seat cushion. Combined with the rebound response detection unit, the sponge's rebound recovery shape is obtained after unloading, thus obtaining the initial indentation assessment result.

[0010] The horizontal projection shortening length is calculated based on the instantaneous depression profile and the sponge rebound recovery shape. The part that exceeds the elastic recovery limit is identified as a sign of permanent collapse, and the forward stroke adjustment range is obtained.

[0011] Match the shortened length of the horizontal projection with the adjustment range of the forward stroke, and determine the necessary forward push of the slide rail corresponding to the area where the permanent collapse signs are located as the seat depth adjustment scheme.

[0012] Extract the target range of horizontal projection length from the seat depth adjustment scheme, simultaneously obtain the actual support shape of the thigh and the gap state between the end of the thigh support and the back of the knee, and determine the parameter combination of the target range, actual support shape and gap state that meets the condition of no compression on the back of the knee as the forward push control signal.

[0013] The slide rail is driven to perform a forward pushing action according to the forward pushing control signal. The horizontal projection length and the state of the gap behind the knee are collected synchronously after the action. Combined with the rebound change, the adjusted sinking recovery seat depth stability is obtained.

[0014] The adjusted seat depth stability is compared with the initial seat depth assessment result. When the horizontal projection length falls into the target range and the gap status behind the knee shows that the end of the thigh support does not touch the back of the knee, the seat depth adjustment result is output, indicating that the seat depth adjustment is completed and there is no compression behind the knee.

[0015] Furthermore, the indentation depth detection unit deployed in zones acquires the instantaneous indentation profile of the sponge at the back of the seat cushion, and combines this with the rebound response detection unit to obtain the sponge's rebound recovery shape after unloading, to obtain the initial indentation assessment result, including:

[0016] Multiple detection areas are divided on the sponge surface at the back of the seat according to the pressure area of ​​the buttocks. An independent indentation depth detection unit is deployed in each detection area to obtain the instantaneous indentation value along the vertical direction of the detection area. The instantaneous indentation value is spliced ​​and aligned according to the spatial coordinates to obtain the instantaneous indentation contour.

[0017] Furthermore, the indentation depth detection unit deployed in zones acquires the instantaneous indentation profile of the sponge at the back of the seat cushion, and combines this with the rebound response detection unit to obtain the sponge's rebound recovery shape after unloading, to obtain the initial indentation assessment result, including:

[0018] After the passenger leaves the seat and the equipment is unloaded, the rebound response detection unit, which is configured in the same partition as the indentation depth detection unit, is activated to sample the sponge rebound in a time sequence, and obtain the rebound height trajectory data of each detection area. When the change in the rebound height trajectory data between adjacent sampling points is lower than the threshold, the position is locked to obtain the sponge rebound recovery shape.

[0019] The difference between the sponge's rebound recovery shape and the instantaneous depression contour is compared according to spatial coordinates, and the results are summarized to form a comparison mapping table as the initial depression assessment result.

[0020] Furthermore, the step of calculating the horizontal projection shortening length based on the instantaneous depression profile and the sponge's rebound recovery shape, identifying portions exceeding the elastic recovery limit as signs of permanent collapse, and determining the forward thrust adjustment range includes:

[0021] The vertical depression amount of each detection area in the instantaneous depression contour and the rebound height position of the same zone are calculated. The difference between the length of the horizontal projection segment under loading conditions and the length of the horizontal projection segment after unloading and stabilization is calculated according to the position of the same zone to obtain the horizontal projection shortening length distributed zone by zone along the front and rear direction of the seat cushion.

[0022] Furthermore, the step of calculating the horizontal projection shortening length based on the instantaneous depression profile and the sponge's rebound recovery shape, identifying portions exceeding the elastic recovery limit as signs of permanent collapse, and determining the forward thrust adjustment range includes:

[0023] For each detection area, the maximum allowable deformation threshold of the sponge that has not undergone permanent deformation under repeated pressure is retrieved as the elastic recovery limit value. The shortened length of the horizontal projection is compared with the elastic recovery limit value in the same area. The minimum forward thrust is extracted from the excess part as the lower limit and the maximum forward thrust is extracted as the upper limit to obtain the forward thrust adjustment range.

[0024] Furthermore, the method of matching the shortened horizontal projection length with the adjustment range of the forward stroke, and determining the necessary forward thrust of the slide rail corresponding to the area where the permanent collapse signs are located as the seat depth adjustment scheme, includes:

[0025] For each of the permanent collapse signs, the horizontal projection shortening length value corresponding to the area is determined to be in interval with the forward stroke adjustment range. The value falling within the interval is used as the forward push amplitude of the slide rail, and is bound to the area of ​​the permanent collapse sign to form a matching mapping table.

[0026] The necessary amplitude sequence for pushing the slide rail forward is obtained by arranging the slide rails according to their positions in the matching mapping table. The largest value in the sequence is taken as the target amplitude, and it is superimposed with the initial position of the slide rail to obtain the target position coordinates. The target position coordinates together with the target amplitude are used as the seat depth adjustment scheme.

[0027] Furthermore, the target range of horizontal projection length is extracted from the seat depth adjustment scheme, and the actual support shape of the thigh and the gap state between the end of the thigh support and the back of the knee are obtained simultaneously. The parameter combination of the target range, actual support shape, and gap state that satisfies the condition of no compression on the back of the knee is determined as the forward push control signal, including:

[0028] The horizontal coordinate value projected along the front-back direction of the target position coordinate in the seat depth adjustment scheme is analyzed, and the horizontal coordinate value is taken as the lower limit endpoint of the target interval, and the sum of the horizontal coordinate value and the target amplitude is taken as the upper limit endpoint of the target interval.

[0029] Furthermore, the target range of horizontal projection length is extracted from the seat depth adjustment scheme, and the actual support shape of the thigh and the gap state between the end of the thigh support and the back of the knee are obtained simultaneously. The parameter combination of the target range, actual support shape, and gap state that satisfies the condition of no compression on the back of the knee is determined as the forward push control signal, including:

[0030] An array of pressure sensors is used to collect data on the pressure distribution of the thigh. The areas that are continuously compressed and whose pressure exceeds a preset threshold are connected to form the actual support shape.

[0031] The infrared ranging probe is activated to measure the distance between the end of the thigh support and the back of the knee, and the gap state is obtained by comparing it with the preset compression critical distance.

[0032] Furthermore, the step of driving the slide rail to perform a forward pushing action according to the forward control signal, simultaneously collecting the horizontal projection length and the state of the gap behind the knee after execution, and combining the rebound change to obtain the adjusted sinking recovery seat depth stability, includes:

[0033] Based on the target position coordinates and target amplitude encapsulated in the forward push control signal, a displacement command is sent to the slide rail drive unit to drive the seat slide rail from the initial position to infinitely approach the target position coordinates. The position encoder sends back the current coordinate value of the slide rail for comparison with the target position coordinates. When the target position coordinates are reached, the forward push operation stops.

[0034] Furthermore, the step of comparing the adjusted seat depth stability with the initial seat depth assessment result, and outputting a seat depth adjustment result indicating that the seat depth adjustment is complete and there is no compression behind the knees when the horizontal projection length falls within the target range and the gap status behind the knees shows that the end of the thigh support does not approach the back of the knees, includes:

[0035] Retrieve the rebound recovery pattern from the initial sinking assessment results, compare the rebound change data in the adjusted sinking recovery seat depth stability with the rebound recovery pattern, mark the current seat depth state as qualified based on the comparison results, and output the seat depth adjustment execution results.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This invention discloses a method for controlling the seat depth adjustment of an ergonomic chair. Addressing the challenges of permanent collapse of the rear foam in the seat cushion during prolonged use, leading to a shortened perceived seat depth, and the tendency for forward adjustment of the sliding rail to cause pressure on the back of the knees, this invention utilizes a zoned, deployed indentation depth detection unit to collect real-time data on the instantaneous collapse profile of the rear foam. Combined with a rebound response detection unit to obtain the rebound recovery shape after unloading, the horizontal projection shortening length is calculated. Areas exceeding the elastic recovery limit are identified as signs of permanent collapse, thus allowing for the calculation of the forward adjustment range. Furthermore, the actual support shape of the occupant's thigh and the gap between the thigh and the back of the knee are simultaneously acquired. The parameter combination that satisfies the condition of no pressure is determined as the forward control signal to drive the sliding rail. The feedback loop is verified by comparing the rebound of the horizontal projection length and the gap state after execution. This invention achieves accurate identification of foam collapse and intelligent matching of the forward adjustment range of the sliding rail, compensating for seat depth loss and avoiding knee pressure, effectively improving posture support stability and riding comfort. Attached Figure Description

[0038] Figure 1 This is a flowchart of a method for adjusting the depth of an ergonomic chair seat cushion according to the present invention.

[0039] Figure 2 This is a schematic diagram of an ergonomic chair seat depth adjustment control method according to the present invention.

[0040] Figure 3 This is another schematic diagram of an ergonomic chair seat depth adjustment control method according to the present invention. Detailed Implementation

[0041] The present invention will now be described in detail through specific embodiments:

[0042] like Figures 1 to 3 This embodiment of an ergonomic chair seat depth adjustment control method may specifically include:

[0043] S101. The indentation depth detection unit deployed in zones collects the instantaneous indentation contour of the sponge at the back of the seat cushion in real time, and combines it with the rebound response detection unit to obtain the sponge's rebound recovery shape after unloading, thus obtaining the initial indentation assessment result.

[0044] The rear foam surface of the seat cushion is divided into multiple detection zones based on the distribution characteristics of the pressure-bearing area of ​​the buttocks. An independent indentation depth detection unit is deployed in each detection zone. Real-time sampling is performed on the deformation of the foam surface under pressure after the occupant sits down to obtain the instantaneous indentation value in the vertical direction of each detection zone.

[0045] By combining the spatial coordinates of the detection area, the instantaneous depression values ​​are spliced ​​and aligned according to their positions, and the depression difference between adjacent detection areas is interpolated to obtain the instantaneous depression profile covering the entire pressure surface of the back of the seat cushion.

[0046] In response to the pressure state corresponding to the instantaneous depression profile, after the passenger leaves the seat and an unloading condition is formed, the rebound response detection unit, which is configured in the same partition as the indentation depth detection unit, is activated to continuously sample the rebound process of the sponge surface after unloading according to the time sequence.

[0047] The trajectory data of the rebound height along the vertical direction of each detection area is acquired over time. When the height change of adjacent sampling points within a preset observation period is lower than a preset threshold, it is determined that the rebound of that area tends to stabilize and the height position at this time is locked, thus obtaining the rebound recovery pattern of each detection area at the rear of the sponge.

[0048] Based on the rebound recovery shape of each detection area at the rear of the sponge, the instantaneous depression contour of the corresponding area is compared with the corresponding spatial coordinate difference to extract the deformation difference of each detection area in the vertical direction under loading and unloading conditions.

[0049] The deformation differences are summarized and arranged according to the location of the detection area to form a reference mapping table reflecting the relationship between the sinking depth and rebound height of each zone at the back of the seat. The reference mapping table is used as the initial sinking assessment result.

[0050] The accuracy of seat depth adjustment in ergonomic chairs depends on precise sensing of the pressure deformation of the rear of the foam. In one embodiment, the rear of the seat cushion is divided into 3 to 5 equidistant grids along both the front-to-back and left-to-right directions, forming multiple independent detection areas.

[0051] Each detection area covers a pressure-bearing surface roughly the size of a coin, serving as the smallest sensing particle.

[0052] In one possible implementation, the detection area is divided based on the distribution characteristics of the transition zone between the ischial tuberosity projection of the buttocks and the root of the thigh. Specifically, the rear of the seat cushion is divided into 3 to 5 grid areas along the front-to-back direction and 3 to 5 grid areas along the left-to-right direction.

[0053] The two rows of grids in the middle near the backrest correspond to the main pressure zone for the buttocks, with a grid spacing of 20 to 30 millimeters in this area. The grids near the front edge of the seat correspond to the groin area, with a grid spacing of 40 to 60 millimeters in this area.

[0054] By employing the aforementioned non-equidistant adaptive segmentation method, higher detection accuracy is achieved in the main pressure-bearing area of ​​the buttocks, while maintaining sufficient coverage in the groin region. The position coordinates of the detection area are calibrated and fixed once before leaving the factory.

[0055] Specifically, a thin-film piezoresistive sensor is embedded at the bottom of each detection area, forming an indentation depth detection unit. The thin-film piezoresistive sensor is attached between the lower surface of the sponge and the base plate. When pressure is applied, the resistance value of the sensitive thin film inside changes linearly with the indentation deformation.

[0056] After conversion by a bridge circuit, the output is an analog voltage signal U, which is positively correlated with the vertical sag and is measured in millivolts. This voltage signal is amplified and filtered by a signal conditioning circuit before being sent to the 12-bit ADC of the acquisition module for digitization.

[0057] Then, based on the conversion relationship calibrated before leaving the factory, h equals k multiplied by U plus b to complete the displacement conversion, where h is the instantaneous indentation in millimeters, k is the calibration slope coefficient, and b is the zero-position offset compensation value. Both are obtained by pre-calibrating each sensor at three standard indentation points: 0 mm, 10 mm, and 20 mm.

[0058] After the passenger is seated, the indentation depth detection unit scans the area area by area with a single-point sampling period of 5 milliseconds, continuously acquiring the instantaneous indentation value h along the vertical direction of each detection area. The acquisition period for a complete bearing surface profile is 5 milliseconds multiplied by the total number of grids.

[0059] In this embodiment, based on 25 grids, the time window required for a complete contour acquisition is 5 times 25 equals 125 milliseconds, making the number of grids consistent with the previous 3 to 5 times 3 to 5.

[0060] It is understandable that the depression value obtained from a single detection area only reflects local deformation, and the depression values ​​of all detection areas need to be spliced ​​together according to the position coordinates specified at the factory.

[0061] The factory-calibrated position coordinates are determined after product assembly by pressing the geometric center of each grid sequentially with a standard pressure head. The number of the corresponding sensing unit in the detection area and its two-dimensional coordinates (x, y) in the seat coordinate system are recorded. A mapping table between the number and the coordinates is then created and stored in the controller's storage area.

[0062] During stitching, the depression amount d of each detection area is first filled into its geometric center points x and y according to the mapping table. For the transition boundary between adjacent grids, the depression amount of the center points of the four adjacent grids is used as known data points. The points to be estimated x0 and y0 are first linearly interpolated along the x direction, and then linearly interpolated along the y direction to obtain the deformation estimate of the point, and the grid gaps are filled.

[0063] By combining the measured values ​​of all grid center points with the estimated values ​​of interpolation points, a two-dimensional depression distribution covering the entire pressure-bearing surface of the back of the seat cushion is formed, which is the instantaneous depression profile corresponding to this sampling period.

[0064] For example, when a passenger gets up and leaves the seat, if the indentation depth detection unit outputs a value of indentation that drops to less than 1.2 times the initial value before pressure is applied within two consecutive sampling cycles, it is determined that the unloading condition has been entered, and the rebound response detection unit is activated.

[0065] The initial value of unpressurized state is the reference value of the indentation depth of the seat surface when it is not under load, which is recorded during the first sampling after the system starts. This reference value is stored in the non-volatile memory of the control unit and serves as a comparison reference for subsequent unloading determination.

[0066] The specific determination process is as follows: The control unit obtains the current subsidence value Dcurrent in real time, reads the stored initial value of no pressure Dinitial, and calculates the difference between the current subsidence value Dcurrent and the initial value of no pressure Dinitial. When Dcurrent minus Dinitial is less than the preset unloading determination increment for two consecutive sampling periods, the unloading condition is confirmed.

[0067] For example, when the initial subsidence is 20% of the unloaded initial subsidence, that is, when D is currently less than or equal to 1.2 times D_initial and D_initial is non-zero, the unloaded condition is confirmed.

[0068] In one embodiment, the rebound response detection unit and the indentation depth detection unit share the same set of grid partitions, but the object of collection is the change in the height of the sponge rebounding after unloading.

[0069] The rebound response detection unit uses laser displacement ranging. The laser emitter is fixedly installed below the base plate supporting the sponge, and the laser beam passes vertically upward through the reserved through hole in the base plate to irradiate the lower surface of the sponge.

[0070] For each detection area, the rebound height along the vertical direction of the area is continuously tracked with a sampling period of 100 milliseconds to obtain trajectory data in the form of a time series. This data contains a sequence of data pairs of timestamps and corresponding height values.

[0071] To determine the stability of trajectory data, the observation period was set to 30 seconds, i.e., 300 consecutive sampling points, and the height change threshold was set to 0.2 mm.

[0072] If the absolute value of the height difference between two adjacent sampling points in a certain detection area is less than 0.2 mm at any time during the observation period, it is determined that the rebound of that area tends to stabilize. At this time, the height value at that moment is recorded as the final recovery height of the area, which will serve as the benchmark reference value for subsequent indentation depth calculations.

[0073] Specifically, a unified vertical coordinate system is established with the initial surface before loading as the zero point. The instantaneous depression depth h of each detection area and the final recovery rebound height r of the same area are aligned according to spatial coordinates and then the difference is calculated.

[0074] Where h is the vertical displacement relative to the initial surface under loading conditions, which is negative due to downward movement, and the unit is millimeters. r is the vertical displacement relative to the initial surface after unloading and stabilization, which is positive due to upward rebound, and the unit is millimeters.

[0075] The residual deformation Δ is equal to h minus r. This value is always negative, and its absolute value represents the depth of permanent plastic deformation that the detected area failed to fully recover in a complete loading and unloading cycle.

[0076] The same position difference comparison is performed on all detection areas one by one to obtain the set of deformation residuals corresponding to the grid positions. This set is used for subsequent material fatigue cumulative damage assessment and load-bearing capacity degradation analysis.

[0077] The deformation data of each detection area at the rear of the seat cushion during loading and unloading is collected in real time by a pressure sensor array. The sinking amount is defined as the maximum vertical displacement of the area relative to the initial plane during loading, and the rebound height is defined as the vertical displacement of the area relative to the initial plane when it returns to a stable state after unloading.

[0078] The deformation difference is calculated as the difference between the depression and the rebound height, i.e., Δh equals h_down minus h_rebound, where Δh is the deformation difference, h_down is the depression, and h_rebound is the rebound height.

[0079] After summarizing the deformation differences corresponding to each detection area into a deformation difference set, the sets are arranged according to the spatial layout of the detection areas at the back of the seat cushion, with rows corresponding to the left and right grid numbers and columns corresponding to the front and back grid numbers. Each cell records three indicators for that area: the amount of depression, the rebound height, and the deformation difference, forming a comparison mapping table.

[0080] For example, the deformation difference between the two rows of grids near the middle of the backrest is usually 8 to 12 millimeters, while the deformation difference between the grids near the front edge of the seat is generally less than 3 millimeters.

[0081] The mapping table identifies each partition by row and column number, and three fields are recorded under each grid cell: instantaneous depression profile, which is the depression depth of each partition relative to the initial plane at the moment of loading stabilization; rebound recovery shape, which is the height value locked by each partition when the height change of adjacent sampling points within a 30-second observation period after unloading is less than 0.2 mm and the rebound is determined to be stable; deformation difference, which is the difference between the above two values.

[0082] The above-mentioned comparison mapping table is referred to as the initial sinking assessment result. It and the comparison mapping table are different names for the same data set. The former emphasizes the assessment semantics, while the latter emphasizes the data organization form.

[0083] The initial sinking assessment results can intuitively reflect the spatial distribution relationship between the sinking depth and rebound height of each zone at the back of the seat.

[0084] S102. Calculate the horizontal projection shortening length based on the instantaneous depression profile and the sponge's rebound recovery shape. Identify the parts where the horizontal projection shortening length exceeds the elastic recovery limit as signs of permanent collapse, and thus determine the forward stroke adjustment range.

[0085] By acquiring the vertical depression value of each detection area in the instantaneous depression profile and combining it with the rebound height position of the same partition in the rebound recovery pattern, the length of the pressure-bearing surface segment projected onto the horizontal plane along the front-back direction of the seat cushion for each detection area is calculated.

[0086] The difference between the length of the horizontal projection segment under loading conditions and the length of the horizontal projection segment after unloading and stabilization is calculated according to the same partition position. The difference in the length of the projection segment between adjacent detection areas is arranged and connected in spatial order to obtain the shortened length of the horizontal projection distributed in each zone along the front-to-back direction of the seat cushion.

[0087] Based on the shortened length of the horizontal projection, the maximum allowable deformation threshold of the sponge under repeated pressure conditions without permanent deformation is retrieved for each detection area and used as the elastic recovery limit value of that area.

[0088] The shortened horizontal projection length is compared with the corresponding elastic recovery limit value in the same area. If the shortened horizontal projection length of a certain detection area exceeds the elastic recovery limit value of that area, the area is marked as a permanent collapse indication location, and its position coordinates in the front-back direction at the rear of the seat are recorded to obtain a list of permanent collapse indication locations.

[0089] Based on the distribution list of permanent collapse indication locations, for each permanent collapse indication location in the list, the shortened horizontal projection length corresponding to that location is directly used as the forward displacement value of that location.

[0090] The forward thrust values ​​of all permanent collapse signs are summarized according to their location. The minimum forward thrust is extracted as the lower limit and the maximum forward thrust is extracted as the upper limit from the summary results to obtain the forward thrust adjustment range of the seat slide rail.

[0091] The precision of adjusting the seat depth of an ergonomic chair depends on a quantitative understanding of the difference between the deformation of the back of the foam under pressure and its rebound after unloading.

[0092] In one implementation, the instantaneous sinking profile and rebound recovery shape in the aforementioned initial sinking assessment results are used to further deduce the change in the horizontal projection of the seat cushion along the front-to-back direction, which serves as the basis for determining permanent collapse.

[0093] Specifically, the calculation of the horizontal projection shortening length follows the following principle: when the occupant sits down and loads the load, a certain detection area at the back of the sponge sinks by h in the vertical direction. The original length of the pressure-bearing section covered by the detection area along the front-to-back direction of the seat cushion is L0. After sinking, the length of the projection section of this pressure-bearing section on the horizontal plane becomes L1.

[0094] After the passenger disembarks and the load stabilizes, the same detection area rebounds to height position r, and the corresponding horizontal projection segment length becomes L2. The difference between L1 and L2 is calculated according to the same partition position, and the formula is ΔL=L1-L2, where ΔL is the horizontal projection shortening length of the detection area. A positive value indicates the amount of reduction caused by the bearing surface segment not fully recovering in the horizontal direction during the loading and unloading cycle.

[0095] The entire detection area at the rear of the sponge was calculated one by one to obtain a set of ΔL values ​​that correspond one-to-one with the grid position.

[0096] Furthermore, the ΔL values ​​of adjacent detection areas are connected by linear interpolation according to the spatial order in the front-back direction, forming a distribution curve that undulates along the front-back direction of the seat cushion for visual monitoring of the sponge performance change trend. The vertical axis of the curve is the shortened length of the horizontal projection, and the horizontal axis is the relative position of the detection area on the seat cushion.

[0097] In one possible implementation, the elastic recovery limit value needs to be pre-calibrated according to the grade of the sponge material before the chair leaves the factory. The calibration method is as follows: Select a sample of the sponge material to be tested, and apply a 75 kg load to the sample for 30 seconds using a standard loading device under the conditions of a standard laboratory ambient temperature of 23 degrees Celsius and a humidity of 50%, and then unload it.

[0098] After standing for 120 seconds, measure the horizontal projection shortening length ΔL of the same detection area. Repeat the loading and unloading cycle 50 times and record the ΔL value after each cycle.

[0099] When the fluctuation range of ΔL value is less than 0.2 mm for 5 consecutive cycles, it is considered stable, and the average value of ΔL for the last 10 cycles is taken as the elastic recovery limit value of the material.

[0100] For polyurethane foam with a density of 30 to 35 kg / m³, the elastic recovery limit is typically 1.5 to 2.5 mm; for materials with a density of 35 to 40 kg / m³, the corresponding limit is 1.0 to 1.8 mm; and for high-density foam with a density of 40 kg / m³ or more, the limit is 0.5 to 1.2 mm.

[0101] Specifically, sponge samples from the same batch were placed on a pressure testing bench and cyclically loaded at different pressure levels. The residual deformation of the sample after rebound at each loading level was recorded. The deformation value corresponding to the first entry of this residual into the irreversible region was taken as the elastic recovery limit value of that grade of sponge.

[0102] The elastic recovery limit value was measured according to the aforementioned unified calibration method of 75 kg load and 50 cycles, and was graded according to material and density: 1.5 to 2.5 mm for ordinary polyurethane foam with a density of 30 to 35 kg per cubic meter, 1.0 to 1.8 mm for a density of 35 to 40 kg per cubic meter, and 0.5 to 1.2 mm for high-density polyurethane foam with a density of more than 40 kg per cubic meter.

[0103] Because memory foam has a slow viscoelastic recovery, it is calibrated individually with a thickness of 3 to 5 millimeters. The elastic recovery limit value of each test area is bound to the corresponding grid number and solidified into the storage unit of the chair control board in the form of a single numerical value, which is used for subsequent direct numerical comparison with ΔL for judgment.

[0104] It should be noted that the horizontal projection shortening length ΔL refers to the difference between the horizontal projection length L1 of the same bearing surface segment when it stabilizes after loading and sinking and the horizontal projection length L2 after unloading and rebounding. It is obtained by equating ΔL to L1 minus L2, and reflects the irreversible reduction of the bearing surface segment in the horizontal direction after one loading and unloading cycle.

[0105] The elastic recovery limit value is the upper limit of reversible deformation calibrated in advance through loading and unloading tests for the same bearing surface segment and the same horizontal direction. Within this value range, the horizontal projection length of the bearing surface segment can be restored to more than 98 times the 0 point of L0 after unloading; if the value is exceeded, the deformation cannot be fully recovered.

[0106] Since both refer to the same change in length of the same pressure-bearing surface segment in the horizontal direction, and their dimensions are consistent with the direction of action, they can be directly compared numerically within the same detection area.

[0107] If the measured ΔL in the area is greater than the pre-calibrated elastic recovery limit value, for example, if the limit value is 2.5 mm and the measured ΔL reaches 3.2 mm, then it is determined that the horizontal reduction of the bearing surface section in the area has exceeded the range of reversible deformation of the material, and the area is marked as a location with signs of permanent collapse.

[0108] Preferably, the position coordinates of each permanent subsidence indication location on the rear of the seat cushion along the front-to-back direction are recorded, with the coordinates measured in millimeters relative to the front edge of the seat cushion. The position coordinates of all marked locations are compiled in front-to-back order to obtain a list of the distribution of permanent subsidence indication locations.

[0109] It is understandable that the horizontal projection shortening length ΔL corresponding to the location of permanent collapse is itself a representation of the irreversible reduction in the length of the pressure-bearing section along the front-back direction of that location.

[0110] In one embodiment, the ΔL value of each permanent collapse indication location is determined by interval analysis and then mapped to the forward thrust value d that the seat rail needs to compensate for at that location.

[0111] Specifically, a lower threshold d is set. min 2 mm, upper limit threshold d max It is 15 mm. When ΔL is less than d min When the collapse is considered to be within the normal wear and tear range, this part is not included in the compensation, and d is taken as 0; when ΔL is greater than d max At that time, it was determined that the collapse had exceeded the adjustable travel of the slide rail, so d was pressed. max Cut-off; when ΔL is at d min With d max When d is between ΔL and ΔL, it means that a one-to-one equivalence mapping relationship is maintained within the effective interval.

[0112] This segmented processing method ensures that the forward push can reflect the actual degree of collapse while avoiding ineffective compensation and overtravel.

[0113] For example, if the ΔL of a certain permanent collapse site is 4 mm, then the forward thrust value corresponding to that site is also 4 mm.

[0114] Furthermore, the forward amplitude values ​​of all permanent collapse indication locations in the distribution list are summarized according to their location. The forward amplitude with the smallest value is extracted from the summary results as the lower limit of the actual measurement, and the forward amplitude with the largest value is extracted as the upper limit of the actual measurement.

[0115] The system pre-stores a standard forward travel adjustment range based on historical occupant data statistics. The lower limit of this standard range is 2 mm and the upper limit is 15 mm.

[0116] The measured lower limit is compared with the lower limit of the standard range, and the measured upper limit is compared with the upper limit of the standard range. If the measured lower limit is less than the lower limit of the standard range or the measured upper limit is greater than the upper limit of the standard range, the occupant's body shape characteristics are determined to be outside the normal adaptation range. The system issues an early warning and uses the standard range as the final adjustment range.

[0117] If the measured values ​​all fall within the standard range, the lower and upper limits of the measured values ​​will be used as the final adjustment range to provide an optional forward thrust range for the subsequent slide rail actuator.

[0118] S103. Match the shortened length of the horizontal projection with the adjustment range of the forward stroke, and determine the necessary forward push of the slide rail corresponding to the area where the permanent collapse signs are located as the seat depth adjustment scheme.

[0119] By acquiring the distribution data of the horizontal projection shortening length along the front-to-back direction of the seat cushion, and retrieving the lower and upper limits of the forward thrust adjustment range, the horizontal projection shortening length value corresponding to each permanent collapse sign location is used to determine the interval affiliation of the horizontal projection shortening length value and the forward thrust adjustment range.

[0120] If the horizontal projection shortening length value falls within the forward stroke adjustment range, then the value is determined as the slide rail forward thrust amplitude for that part, and the slide rail forward thrust amplitude is bound to the permanent collapse indication part one by one to obtain a matching mapping table between the permanent collapse indication part and the slide rail forward thrust amplitude.

[0121] According to the matching mapping table of permanent collapse indication locations and slide rail forward thrust amplitude, for each permanent collapse indication location in the matching mapping table, the slide rail forward thrust amplitude value bound to that location is extracted from the matching mapping table, and the slide rail forward thrust amplitude value is used as the necessary amplitude to compensate for the permanent collapse of that location.

[0122] The necessary amplitudes for all permanent collapse indication locations are arranged in order of their position along the front-back direction, resulting in the sequence of necessary amplitudes for the slide rail to be pushed forward for the areas with permanent collapse indications.

[0123] Based on the necessary amplitude sequence of the slide rail forward push, for each permanent collapse indication area in the sequence, the necessary amplitude with the largest value in the sequence is taken as the target amplitude of the slide rail forward push. The target amplitude is then superimposed with the current initial position of the seat cushion slide rail to obtain the target position coordinates when the slide rail is pushed forward. The target position coordinates together with the target amplitude are used to determine the seat depth adjustment scheme.

[0124] The final implementation of ergonomic chair seat depth adjustment relies on converting the deformation information of the aforementioned permanently collapsed areas into displacement commands that the slide rail can execute. In one implementation, the process of deriving the seat depth adjustment scheme follows a progressive logic of matching-extraction-determination. By using the aforementioned zone-by-zone distribution data of the horizontal projection shortening length and the boundary values ​​of the forward stroke adjustment range, the final displacement amount that the slide rail needs to execute is gradually derived.

[0125] Specifically, the implementation details of the interval attribution determination are as follows: the chair control board reads the pre-calibrated forward travel adjustment range, including the lower limit value d, from the non-volatile storage unit of the control system via the internal communication bus. min and upper limit value d maxThis range has been determined based on historical valid subsidence data. The control panel simultaneously reads the horizontal projection shortening length value d of each currently detected permanent subsidence indicator location.

[0126] For each part, perform the following attribution determination: when d is less than d min At that time, the deformation of this part is within the elastic recovery range of the material and does not trigger the compensation mechanism. The data of this part is marked as invalid and removed from subsequent processing.

[0127] When d is in d min to d max When the deformation of the part is within the compensable range, the value d is used as the forward push command value of the corresponding slide rail.

[0128] When d is greater than d max At that time, the collapse of this part had exceeded the mechanical travel capacity of a single adjustment, according to the upper limit value d. max Perform truncation and record the out-of-limit flag.

[0129] After determining the location, the chair control board generates drive commands only for areas deemed within the compensation range, sending the corresponding forward thrust value to the stepper motor driver of each area's slide rail. For example, if the d value for a certain detection area is 3.5 mm, d... min 2 mm, d max If the value is 8 mm, then 3.5 mm is directly used as the forward push amplitude of the slide rail in that part.

[0130] Furthermore, for each permanent collapse indication location falling into the interval, a record is created by combining the grid number of the location with the corresponding slide rail advance amplitude value. All records are compiled into the matching mapping table. Each row of the matching mapping table corresponds to a permanent collapse indication location, and the column fields include three items: grid number, location coordinates, and slide rail advance amplitude. This table is maintained by the chair control board and is available for subsequent modules to read at any time.

[0131] It is understandable that the slide rail advance amplitude in the matching mapping table is the displacement necessary to compensate for the permanent collapse of the part. Therefore, the slide rail advance amplitude value of each record is directly extracted as the necessary amplitude for that part.

[0132] In one embodiment, permanent signs of collapse on the surface of the seat cushion are detected by image recognition or pressure sensors. A coordinate system is established with the front edge of the seat cushion as the origin, and the position coordinates of each collapsed part along the front-rear direction of the seat cushion are measured. The coordinate values ​​are in millimeters, and the larger the value, the closer it is to the rear end of the seat cushion.

[0133] Based on the ascending order of the coordinate values ​​of the permanent sagging areas (from the front to the back of the seat cushion), the necessary amplitude corresponding to each sagging area is arranged one by one to form a sequence of necessary amplitudes for the slide rail to advance. This sequence is used to guide the phased control of the slide rail's forward movement. For example, permanent sagging areas near the backrest are placed at the beginning of the sequence, while those near the front edge of the seat are placed at the end. The length of the sequence is equal to the number of permanent sagging areas.

[0134] Preferably, the target amplitude is determined according to the following principle: Since the seat slide rail adopts an integral sliding mechanism, that is, the slide rail and the seat frame are connected as a whole and move forward synchronously, this structure cannot independently set the forward push distance for different areas of the seat. Therefore, it is necessary to extract the maximum collapse amplitude value from the detection sequence as the overall forward push amount to ensure that the area with the most severe collapse receives sufficient deformation compensation, while ensuring that other areas do not have residual collapse due to insufficient forward push amount.

[0135] Specifically, the necessary amplitude sequence for advancing the slide rail is compared item by item, and the largest value is taken as the target amplitude, denoted as F. For example, if a sequence contains three necessary amplitude values, namely 2.8 mm, 4.2 mm, and 3.6 mm, then 4.2 mm is taken as the target amplitude F.

[0136] In another embodiment, if all necessary amplitude values ​​in the sequence are the same, then the common value is the target amplitude F.

[0137] Furthermore, the target amplitude F is superimposed with the current initial position of the seat rail. The initial position is obtained by a position encoder installed on the fixed end of the rail. This encoder is a photoelectric absolute encoder with a resolution of 0.1 mm, which can output the horizontal displacement coordinates of the rail relative to the center point of the front edge of the seat base in real time. This center point of the front edge is the origin of the coordinate system, with the direction of vehicle movement as the positive direction.

[0138] The initial position coordinates of the slide rail before the forward push is triggered are marked as P0, in millimeters. The target position coordinates P1 that the slide rail should reach after the forward push are obtained by superposition calculation. The calculation relationship is P1=P0+F, where P1 and P0 are both horizontal coordinates relative to the center point of the front edge of the seat base, and F is the aforementioned target amplitude. All three are in millimeters and are directly added together.

[0139] It should be noted that the target position coordinates P1 and the target amplitude F are packaged together as a seat depth adjustment scheme, which is written into the instruction cache by the chair control board. In the seat depth adjustment scheme, P1 is used for position closed-loop control, and F is used for displacement stroke verification. The two constitute the complete drive instruction of the slide rail actuator, thereby completing the seat depth adjustment decision-making process corresponding to the permanent collapse indication area.

[0140] S104. Extract the target range of horizontal projection length from the seat depth adjustment scheme, and simultaneously obtain the actual support shape of the occupant's thigh on the seat cushion and the gap state between the end of the thigh support and the back of the knee. Determine the parameter combination that satisfies the condition of no compression on the back of the knee as the forward push control signal.

[0141] By acquiring the target position coordinates and target amplitude data stored in the seat depth adjustment scheme, the horizontal coordinate value of the target position coordinates projected along the front-back direction in the seat cushion base coordinate system is analyzed. The horizontal coordinate value is used as the lower limit endpoint of the target interval, and the sum of the horizontal coordinate value and the target amplitude is used as the upper limit endpoint of the target interval.

[0142] Connect the lower limit endpoint and the upper limit endpoint along the front-back direction to form the target interval of the horizontal projection length. Write the lower limit endpoint, the upper limit endpoint, and the interval span of the target interval into a temporary cache to obtain the target interval of the horizontal projection length for subsequent condition matching calls.

[0143] For the seat depth state corresponding to the target range of the horizontal projection length, the pressure distribution data of the passenger's thighs falling on the seat is collected by the array pressure sensor on the surface of the seat. The parts of the pressure distribution data that are continuously pressed along the front-back direction of the seat and whose pressure exceeds the preset pressure threshold are connected to form the actual support shape of the thighs on the seat, and the end position of the actual support shape in the front-back direction is marked.

[0144] The infrared ranging probe above the front edge of the seat cushion is activated simultaneously, scanning forward and measuring the distance between the end of the thigh support and the back of the knee in the front-back direction. The distance is then compared with a preset compression critical distance to obtain the gap between the end of the thigh support and the back of the knee.

[0145] Based on the target range of the horizontal projection length, the actual support shape, and the gap state, the pre-established judgment condition for no compression on the back of the knee is retrieved. The judgment condition requires that the span between the lower and upper limits of the target range falls within the front and rear pressure span of the actual support shape, the end of the actual support shape does not exceed the preset limit position of the front edge of the seat in the front and rear direction, and the gap state display distance value is greater than the preset compression critical distance.

[0146] The target position coordinates and target amplitude in the seat depth adjustment scheme are substituted into the judgment conditions for compliance verification. If the target interval, the actual support form and the gap state all meet the judgment conditions, the target position coordinates and the target amplitude are packaged together and determined as the forward push control signal.

[0147] Before the ergonomic chair pushes forward along the slide rails, the feasibility of the aforementioned seat depth adjustment scheme needs to be verified a second time to avoid squeezing the back of the occupant's knees. In one embodiment, the forward push control signal is generated through four steps: target interval extraction, support shape acquisition, gap state measurement, and three condition verifications, and is finally encapsulated and output by the chair control board.

[0148] Specifically, the extraction process of the target range of the horizontal projection length is as follows: when the chair control board executes step S104, it reads the seat depth adjustment scheme from the instruction cache and parses out the target position coordinates P1 and the target amplitude F.

[0149] Based on the coordinate system of the seat base plate, the target range of horizontal projection length x1 to x2 is determined by taking the measured horizontal projection length L0 before pushing forward as the lower limit endpoint x1 and L0 plus the target amplitude F as the upper limit endpoint x2. This range and the measured horizontal projection length L' after execution are both in the dimension of the pressure section length and can be directly compared.

[0150] This range defines the horizontal projection length of the front end of the seat cushion that should be reached when the push control signal is active. The chair control panel uses this range to determine when the push motor should stop driving. For example, in a specific scenario, if the horizontal component of P1 in the front-to-back direction is 120 mm and F is 4.2 mm, then the target range is 120 to 124.2 mm.

[0151] Furthermore, for the seat depth state corresponding to the target range, an array of pressure sensors is used to collect pressure distribution data. The array of pressure sensors is laid out in a grid pattern under the surface of the seat cushion, with the spacing between adjacent sensing units set to 10 to 15 millimeters. Each sensing unit independently outputs the pressure reading at that location.

[0152] After the passenger is seated, all sensing units simultaneously sample a frame of pressure distribution data. Specifically, the typical range of average pressure on the bottom of an adult's thigh when sitting is 15 to 25 kPa. In this scheme, 20 kPa is taken as the reference value, and the preset pressure threshold Pth is set to 0.6 times the reference value, i.e., 12 kPa.

[0153] The pressure reading of each sensing unit is compared with Pth. If the reading is greater than or equal to Pth, the position of that sensing unit is marked as a pressure point. All pressure points are clustered according to their spatial adjacency using the 8-connected-domain labeling method. The 8-connected-domain labeling method merges horizontally, vertically, and diagonally adjacent pressure points into connected regions, and the connected region with the largest output area is taken as the actual support shape of the thigh on the cushion.

[0154] The actual support form is recorded with three geometric parameters: starting position, ending position, and front-to-back span. The starting position is the front-to-back coordinate value of the foremost bearing point in the region, the ending position is the front-to-back coordinate value of the last bearing point in the region, and the front-to-back span is the coordinate difference between the ending position and the starting position.

[0155] For example, the actual support profile of a occupant is obtained through a pressure sensor array within the seat cushion. This sensor array is evenly distributed along the front-to-back direction of the seat cushion, with measurement intervals of 10 millimeters. When the pressure value measured by a sensor exceeds a preset pressure threshold Pth, i.e., 12 kPa, it is determined that there is effective support at that location.

[0156] The starting position xs is defined as the sensor position where the first pressure value exceeds 12 kPa when scanning from the rear of the seat forward, and the ending position xe is defined as the sensor position where the first pressure value exceeds 12 kPa when scanning from the front of the seat backward. The front-to-back span of the support structure L = xe - xs.

[0157] For example, if a passenger's starting position xs is 40 mm from the rear of the seat and their ending position xe is 280 mm from the front of the seat, then the front-to-back span L is 240 mm. It should be noted that the ending position xe is uniformly defined as the coordinate of the pressure point closest to the front edge of the seat in the front-to-back direction, serving as a reference point for subsequent gap measurements.

[0158] The actual support configuration described above terminates at 280 mm from the front of the seat cushion. This is merely an example of the specific value of xe in this embodiment, meaning that xe is measured to be 280 mm under this condition, and is not a limitation on the definition of xe itself. Under different body types, different seat cushion sizes, or different pressure distributions, the measured value of xe will vary depending on the actual position of the leading edge of the pressure-bearing area, typically falling within the range of 240 mm to 300 mm from the front of the seat cushion. Specifically, it is based on the center coordinates of the foremost effective pressure-bearing unit acquired by the pressure sensing matrix.

[0159] Understandably, the gap between the end of the thigh support and the back of the knee is collected using an infrared ranging probe mounted above the front edge of the seat cushion. The infrared ranging probe scans an infrared beam forward at a period of 50 milliseconds, with its detection axis angled diagonally downwards, towards the end position xe. It receives the reflected echo from the back of the knee and calculates the distance g between xe and the back of the knee in the front-back direction based on the time of flight.

[0160] Preferably, the preset critical extrusion distance gth is set to 15 mm. If the distance value g is greater than gth, the gap status is marked as sufficient; if g is equal to or less than gth, the gap status is marked as close.

[0161] In one embodiment, the target interval, the actual support shape, and the gap state are simultaneously verified using a condition for determining no compression behind the knee. The condition consists of three sub-conditions: the first sub-condition requires that the entire target interval x1 to x2 fall within the span from the beginning to the end position xe of the actual support shape.

[0162] The second sub-condition requires that the end position xe does not exceed the preset limit position xlim of the front edge of the seat cushion, which is fixed in the storage unit before leaving the factory; the third sub-condition requires that the gap is sufficient. When all three sub-conditions are met, it is determined that there is no risk of compression on the back of the knee.

[0163] If any of the above three sub-conditions are not met, the seat depth adjustment scheme is marked as pending correction, triggering the amplitude contraction mechanism. Specifically, the chair control panel contracts the currently calculated forward thrust amplitude F by a coefficient of 0.8 to obtain the corrected amplitude F' = F × 0.8. At the same time, it recalculates the target position coordinates P1' = P0 + F' using the same coordinate reference as S103, where P0 is the initial position coordinate before the slide rail forward thrust is triggered.

[0164] Subsequently, based on the corrected F' and P1', the safety distance verification, travel boundary verification, and collision risk verification are performed again until all three sub-conditions are met. When all three sub-conditions are met, the chair control board packages the finally confirmed target position coordinates P1 and target amplitude F together, adds a verification pass flag, and generates a forward push control signal.

[0165] The signal is transmitted via the CAN bus between the chair control panel and the slide rail drive unit. After receiving the control signal, the slide rail drive unit drives the stepper motor to control the slide rail to move forward a corresponding distance according to the target amplitude F, so as to achieve the adjustment effect that the seat depth reduction ΔD is equal to F, where ΔD represents the reduction of the effective seat depth in millimeters.

[0166] Throughout the entire process, the slide rail drive unit provides real-time feedback on the current displacement, and the chair control panel monitors the deviation between the actual moving distance and the target amplitude F. When the deviation is less than 2 mm, it is determined that the adjustment is in place and a stop command is issued, thereby completing the closed-loop control of seat depth adjustment.

[0167] S105. Drive the slide rail to perform forward pushing action according to the forward pushing control signal, and simultaneously collect the horizontal projection length and the state of the gap behind the knee after execution. Combined with the rebound change, the adjusted sinking recovery seat depth stability is obtained.

[0168] Based on the target position coordinates and target amplitude encapsulated in the forward control signal, a displacement command is sent to the slide rail drive unit. Upon receiving the command, the drive unit drives the seat slide rail to approach the target position coordinates from its initial position at a constant speed along the forward-backward direction. During this movement, the position encoder transmits the current coordinate value of the slide rail in real time, and the coordinate value is synchronously compared with the target position coordinates.

[0169] When the coordinate value reaches the target position coordinate, the forward pushing action of the slide rail is stopped, and the actual stopping coordinate of the slide rail after completing the forward pushing action is obtained.

[0170] To determine the seat depth state re-established by the slide rail under the actual stopping coordinates, the pressure distribution data of the thigh surface array pressure sensors are activated again. The pressure distribution data is then projected onto the horizontal plane along the front-to-back direction of the seat cushion to obtain the horizontal projection length after execution.

[0171] The infrared ranging probe above the front edge of the seat cushion is activated simultaneously, scanning forward and recording the distance between the end of the thigh support and the back of the knee in the front-back direction. This distance is then compared to a preset critical compression distance to determine the gap state behind the knee after the compression is performed.

[0172] Based on the horizontal projection length after execution, the state of the gap behind the knee, and the rebound change data obtained by the rebound response detection unit after resampling the rebound height of each detection area at the rear of the seat after the forward push, three comparisons are performed. The horizontal projection length after execution is compared with the target interval; the distance value displayed for the gap behind the knee is compared with the preset compression critical distance; and the rebound change data is compared with the rebound recovery pattern in the initial sinking assessment result.

[0173] If all three comparison results are within the preset tolerance range, the adjusted sinking recovery depth stability is obtained.

[0174] After verifying the seat depth adjustment scheme, the ergonomic chair enters the actual execution and post-execution stability evaluation stage. In one embodiment, the chair control board sends the forward push control signal to the slide rail drive unit, driving the slide rail to complete the displacement, and then samples the seat surface state, gap state, and sponge rebound state after execution, finally summarizing to obtain the adjusted sinking recovery seat depth stability.

[0175] Specifically, after receiving the forward control signal, the slide rail drive unit analyzes the target position coordinates P1 and the target amplitude F encapsulated within it. The drive unit uses a stepper motor to drive the slide rail to advance at a constant speed in the forward and backward direction, with the advancing speed set to 3 to 5 millimeters per second to avoid sudden impacts.

[0176] An incremental position encoder is installed on the seat cushion slide rail, which transmits the current coordinate value of the slide rail at a period of 10 milliseconds, denoted as Pcur. The chair control panel calculates the difference between Pcur and P1, and records the difference as ΔP, where ΔP = Pcur - P1.

[0177] When the absolute value of ΔP is less than 0.2 mm for the first time, the slide rail is considered to be in place, ensuring reasonable parameter matching. Specifically, twice the encoder resolution of 0.1 mm is used, covering the maximum theoretical displacement of 0.15 mm within three sampling periods.

[0178] In one embodiment, the last frame coordinate value read by the position encoder when the slide rail stops is the actual stopping coordinate P2. The actual stopping coordinate P2 is written into the retrieval cache as the position reference for subsequent acquisition and comparison.

[0179] Furthermore, after the P2 state stabilizes for 2 to 3 seconds, the chair control panel reactivates the aforementioned array of pressure sensors to sample the pressure distribution data on the bottom of the occupant's thighs. Specifically, the pressure reading of each sensor unit is compared with a preset pressure threshold Pth, and the positions of sensor units with pressure exceeding Pth and adjacent along the front-to-back direction of the seat cushion are marked as pressure points. All pressure points are projected onto a horizontal plane to form a pressure line segment, and the length of the pressure line segment is the horizontal projection length L′ after execution.

[0180] For example, the horizontal projection length before the push is 220 mm, and the lower limit of the target interval is 225 mm and the upper limit is 230 mm. The target amplitude F still uses the value determined in step S103, which is obtained by taking the maximum value of the necessary amplitude sequence of the permanent collapse indication location. In this embodiment, F takes the maximum value of the sequence. The horizontal projection length L′ collected after the push should fall within the target interval [x1, x2], indicating that the push adjustment is effective.

[0181] Understandably, the gap status behind the knee after execution is obtained by a second scan from an infrared ranging probe located above the front edge of the seat cushion. The infrared ranging probe reads the distance value g′ between the end of the thigh support and the back of the knee, and compares g′ with a preset compression critical distance gth. If g′ > gth, the gap status indicates ample space. If g′ ≤ gth, the gap status indicates near-miss.

[0182] It should be noted that after the forward push is completed, the aforementioned rebound response detection unit resamples the vertical rebound height of each detection area at the rear of the seat cushion, recording the latest rebound height r′ for each zone. The difference between r′ and the rebound height r of the same zone saved in the initial sinking assessment result is used to obtain the rebound change data Δr. This rebound change data reflects the magnitude of the change in the rebound shape of the rear of the sponge before and after the forward push.

[0183] Preferably, the three comparisons are performed as follows: the first comparison is made with L′ and the target interval [x1, x2] to determine whether L′ satisfies x1≤L′ <= x2; the second comparison is made with g′ and gth to determine whether g′ is greater than gth; the third comparison is made with the absolute value of Δr and the preset tolerance limit ε to determine whether the absolute value of Δr for each partition is less than ε.

[0184] For example, ε is taken as 0.5 mm. In one embodiment, the three determination results are aggregated into a triplet. When each item in the triplet is true, the chair control board packages the actual stopping coordinate P2, the horizontal projection length L′, and the rebound change data Δr together with the triplet, determines it as the adjusted sinking recovery seat depth stability, and writes it into the chair control board's status register as a stability certificate of the seat depth adjustment execution result for this round.

[0185] S106. Compare the adjusted seat depth stability with the initial seat depth assessment result. When the horizontal projection length falls into the target range after execution and the gap status of the back of the knee shows that the end of the thigh support does not approach the back of the knee, output the seat depth adjustment execution result that the seat depth adjustment is completed and there is no compression on the back of the knee.

[0186] Based on the adjusted depression recovery seat depth stability, the rebound recovery pattern in the initial depression assessment result is retrieved. The rebound change data in the adjusted depression recovery seat depth stability is compared with the rebound recovery pattern, and the horizontal projection length and the state of the posterior knee gap after execution are extracted simultaneously to obtain the comparison result of the changes before and after.

[0187] Based on the comparison results, if the horizontal projection length after execution falls within the target range and the gap status behind the knee shows that the end of the thigh support does not approach the back of the knee, then the current seat depth status is marked as a qualified state where the seat depth adjustment is completed and there is no pressure behind the knee, and the seat depth adjustment execution result is output.

[0188] After the ergonomic chair completes the stability recovery sampling after the adjustment, it enters the final judgment stage of the seat depth adjustment closed loop. In one embodiment, the chair control panel retrieves the rebound change data carried by the adjusted sinking and seat depth stability, the horizontal projection length after the adjustment, and the state of the gap behind the knees, and compares them with the rebound recovery pattern saved in the initial sinking assessment results to obtain the comparison result reflecting the change range of the rebound pattern of the rear part of the foam before and after pushing forward.

[0189] Specifically, the dual-condition determination is implemented as follows: the first condition is that the horizontal projection length L′ after execution must satisfy x1 less than or equal to L′ less than or equal to x2, where x1 and x2 are the lower limit endpoint and upper limit endpoint of the target interval, respectively; the second condition is that the distance value g′ displayed in the gap state behind the knee must be greater than the preset compression critical distance gth, thereby indicating that the end of the thigh support has not yet approached the back of the knee.

[0190] Preferably, the chair control panel needs to be calibrated with a safe clearance threshold gth behind the knee before leaving the factory. This threshold is calibrated to 15 mm based on the anatomical structure of the back of an adult's knee, meaning that there must be a gap of at least 15 mm between the front edge of the seat and the back of the user's knee to avoid compression.

[0191] After the seat depth adjustment is completed by the chair control panel, both the first and second conditions must be met simultaneously to be considered as qualified. The first condition is that the absolute value of the deviation between the actual position coordinates fed back by the seat cushion's fore-and-aft position sensors and the target position coordinates x does not exceed 2 millimeters. The target position coordinates x are set by the user through the control panel or calculated by an intelligent algorithm based on height and body shape.

[0192] The second condition is that the actual gap value dknee measured by the infrared distance sensor at the front edge of the seat cushion behind the knee is not less than gth, that is, dknee is greater than or equal to 15 mm. Here, dknee is the vertical distance between the front edge sensor of the seat cushion and the back of the knee measured in real time.

[0193] During the decision-making process, the chair control panel records the horizontal projection length L after execution. This length L refers to the horizontal distance between the front edge of the seat cushion and the contact surface of the seat back, which is calculated by the difference between two readings from the position sensor.

[0194] The posterior knee space status includes three data points: the actual measured space value dknee, the threshold gth, and a comparison result flag. When dknee is greater than or equal to gth, the flag is set to 1 to indicate safety; otherwise, it is set to 0 to indicate a risk of compression.

[0195] When both the first and second conditions are met, the chair control panel marks the current seat depth status as qualified. It then encapsulates the target position coordinates x, the horizontal projection length L after execution, and the knee posterior gap status, along with the qualified flag, into a seat depth adjustment execution result data packet according to a fixed byte sequence.

[0196] The data packet is stored in hexadecimal format, with a 1-byte pass / fail flag indicating pass. The packaged data packet is written to the execution log area of ​​the chair control panel's built-in flash memory. The log entry includes a timestamp, user ID, adjustment parameters, and verification result, serving as final proof that the seat depth adjustment has been completed without pressure on the back of the knees.

[0197] This certificate can be read by the after-sales service system through the communication interface for fault diagnosis, quality traceability, and analysis of user adjustment habits.

[0198] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for controlling the adjustment of the seat depth of an ergonomic chair, characterized in that, The method includes: The indentation depth detection unit deployed in a zone collects the instantaneous indentation profile of the sponge at the back of the seat cushion. Combined with the rebound response detection unit, the sponge's rebound recovery shape is obtained after unloading, thus obtaining the initial indentation assessment result. The horizontal projection shortening length is calculated based on the instantaneous depression profile and the sponge rebound recovery shape. The part that exceeds the elastic recovery limit is identified as a sign of permanent collapse, and the forward stroke adjustment range is obtained. Match the shortened length of the horizontal projection with the adjustment range of the forward stroke, and determine the necessary forward push of the slide rail corresponding to the area where the permanent collapse signs are located as the seat depth adjustment scheme. Extract the target range of horizontal projection length from the seat depth adjustment scheme, simultaneously obtain the actual support shape of the thigh and the gap state between the end of the thigh support and the back of the knee, and determine the parameter combination of the target range, actual support shape and gap state that meets the condition of no compression on the back of the knee as the forward push control signal. The slide rail is driven to perform a forward pushing action according to the forward pushing control signal. The horizontal projection length and the state of the gap behind the knee are collected synchronously after the action. Combined with the rebound change, the adjusted sinking recovery seat depth stability is obtained. The adjusted seat depth stability is compared with the initial seat depth assessment result. When the horizontal projection length falls into the target range and the gap status behind the knee shows that the end of the thigh support does not touch the back of the knee, the seat depth adjustment result is output, indicating that the seat depth adjustment is completed and there is no compression behind the knee.

2. The method for adjusting and controlling the depth of an ergonomic chair cushion according to claim 1, characterized in that, The indentation depth detection unit, deployed in zones, collects the instantaneous indentation profile of the foam at the back of the seat cushion. Combined with the rebound response detection unit's acquisition of the foam's rebound recovery shape after unloading, an initial indentation assessment result is obtained, including: Multiple detection areas are divided on the sponge surface at the back of the seat according to the pressure area of ​​the buttocks. An independent indentation depth detection unit is deployed in each detection area to obtain the instantaneous indentation value along the vertical direction of the detection area. The instantaneous indentation value is spliced ​​and aligned according to the spatial coordinates to obtain the instantaneous indentation contour.

3. The method for adjusting and controlling the depth of an ergonomic chair cushion according to claim 1, characterized in that, The indentation depth detection unit, deployed in zones, collects the instantaneous indentation profile of the foam at the back of the seat cushion. Combined with the rebound response detection unit's acquisition of the foam's rebound recovery shape after unloading, an initial indentation assessment result is obtained, including: After the passenger leaves the seat and the equipment is unloaded, the rebound response detection unit, which is configured in the same partition as the indentation depth detection unit, is activated to sample the sponge rebound in a time sequence, and obtain the rebound height trajectory data of each detection area. When the change in the rebound height trajectory data between adjacent sampling points is lower than the threshold, the position is locked to obtain the sponge rebound recovery shape. The difference between the sponge's rebound recovery shape and the instantaneous depression contour is compared according to spatial coordinates, and the results are summarized to form a comparison mapping table as the initial depression assessment result.

4. The method for adjusting and controlling the depth of an ergonomic chair cushion according to claim 1, characterized in that, The calculation of the horizontal projection shortening length based on the instantaneous depression profile and the sponge's rebound recovery shape, identifying portions exceeding the elastic recovery limit as signs of permanent collapse, and determining the forward thrust adjustment range includes: The vertical depression amount of each detection area in the instantaneous depression contour and the rebound height position of the same zone are calculated. The difference between the length of the horizontal projection segment under loading conditions and the length of the horizontal projection segment after unloading and stabilization is calculated according to the position of the same zone to obtain the horizontal projection shortening length distributed zone by zone along the front and rear direction of the seat cushion.

5. The method for adjusting and controlling the depth of an ergonomic chair cushion according to claim 1, characterized in that, The calculation of the horizontal projection shortening length based on the instantaneous depression profile and the sponge's rebound recovery shape, identifying portions exceeding the elastic recovery limit as signs of permanent collapse, and determining the forward thrust adjustment range includes: For each detection area, the maximum allowable deformation threshold of the sponge that has not undergone permanent deformation under repeated pressure is retrieved as the elastic recovery limit value. The shortened length of the horizontal projection is compared with the elastic recovery limit value in the same area. The minimum forward thrust is extracted from the excess part as the lower limit and the maximum forward thrust is extracted as the upper limit to obtain the forward thrust adjustment range.

6. The method for adjusting and controlling the depth of an ergonomic chair cushion according to claim 1, characterized in that, The method of matching the shortened horizontal projection length with the adjustment range of the forward stroke, and determining the necessary forward thrust of the slide rail corresponding to the area of ​​permanent collapse as the seat depth adjustment scheme, includes: For each of the permanent collapse signs, the horizontal projection shortening length value corresponding to the area is determined to be in interval with the forward stroke adjustment range. The value falling within the interval is used as the forward push amplitude of the slide rail, and is bound to the area of ​​the permanent collapse sign to form a matching mapping table. The necessary amplitude sequence for pushing the slide rail forward is obtained by arranging the slide rails according to their positions in the matching mapping table. The largest value in the sequence is taken as the target amplitude, and it is superimposed with the initial position of the slide rail to obtain the target position coordinates. The target position coordinates together with the target amplitude are used as the seat depth adjustment scheme.

7. The method for adjusting and controlling the depth of an ergonomic chair cushion according to claim 1, characterized in that, The target range of horizontal projection length is extracted from the seat depth adjustment scheme, and the actual support shape of the thigh and the gap state between the end of the thigh support and the back of the knee are obtained simultaneously. The parameter combination of the target range, actual support shape and gap state that satisfies the condition of no compression on the back of the knee is determined as the forward push control signal, including: The horizontal coordinate value projected along the front-back direction of the target position coordinate in the seat depth adjustment scheme is analyzed, and the horizontal coordinate value is taken as the lower limit endpoint of the target interval, and the sum of the horizontal coordinate value and the target amplitude is taken as the upper limit endpoint of the target interval.

8. The method for adjusting and controlling the depth of an ergonomic chair cushion according to claim 1, characterized in that, The target range of horizontal projection length is extracted from the seat depth adjustment scheme, and the actual support shape of the thigh and the gap state between the end of the thigh support and the back of the knee are obtained simultaneously. The parameter combination of the target range, actual support shape and gap state that satisfies the condition of no compression on the back of the knee is determined as the forward push control signal, including: An array of pressure sensors is used to collect data on the pressure distribution of the thigh. The areas that are continuously compressed and whose pressure exceeds a preset threshold are connected to form the actual support shape. The infrared ranging probe is activated to measure the distance between the end of the thigh support and the back of the knee, and the gap state is obtained by comparing it with the preset compression critical distance.

9. The method for adjusting and controlling the depth of an ergonomic chair cushion according to claim 1, characterized in that, The process of driving the slide rail to perform a forward pushing action according to the forward pushing control signal, simultaneously collecting the horizontal projection length and the state of the gap behind the knee after execution, and combining the rebound change to obtain the adjusted sinking recovery seat depth stability includes: Based on the target position coordinates and target amplitude encapsulated in the forward push control signal, a displacement command is sent to the slide rail drive unit to drive the seat slide rail from the initial position to infinitely approach the target position coordinates. The position encoder sends back the current coordinate value of the slide rail for comparison with the target position coordinates. When the target position coordinates are reached, the forward push operation stops.

10. The method for adjusting and controlling the depth of an ergonomic chair cushion according to claim 1, characterized in that, The process involves comparing the adjusted seat depth stability with the initial seat depth assessment result. After execution, when the horizontal projection length falls within the target range and the posterior knee gap status shows that the thigh support end does not approach the posterior knee, the output shows a completed seat depth adjustment result with no posterior knee compression. This includes: Retrieve the rebound recovery pattern from the initial sinking assessment results, compare the rebound change data in the adjusted sinking recovery seat depth stability with the rebound recovery pattern, mark the current seat depth state as qualified based on the comparison results, and output the seat depth adjustment execution results.

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