Compensation method and system for AMT gear shifting point of electric commercial vehicle

Abstract

The invention belongs to the technical field of vehicle control, and particularly relates to an AMT gear shifting point compensation method and system.The method comprises the steps that firstly, a driver intention signal, a motor state signal and a vehicle operation signal are collected in real time, and effective input data are obtained after preprocessing; a driver intention intensity coefficient representing the power demand urgency degree is calculated through a preset formula, and a temperature influence coefficient reflecting the motor torque output capacity is output by means of the built motor temperature influence model; inputting the coefficient and the preprocessed vehicle operation signal into a comprehensive compensation model to obtain a comprehensive compensation coefficient; and finally, real-time offset compensation is carried out on the standard gear shifting curve based on the coefficient, and a dynamic gear shifting point is generated and transmitted to a gearbox control unit to execute gear shifting. The problem that in the prior art, traditional AMT gear shifting control of an electric commercial vehicle is insufficient in adaptability to complex working conditions can be solved.

Description

Technical Field

[0001] This invention belongs to the field of vehicle control technology, and in particular relates to a method and system for compensating shift points of an AMT (Automated Manual Transmission) in an electric commercial vehicle. Background Technology

[0002] With the rapid development of new energy logistics, engineering transportation and other fields, the market penetration rate of electric commercial vehicles continues to increase. These vehicles are generally equipped with 4-6 speed AMT transmissions to adapt to the power requirements of heavy-duty and long-distance transportation. However, under complex working conditions, the existing AMT shift control technology has exposed many key defects: 1. Poor power performance during uphill driving: When driving on slopes, existing AMT control systems mainly rely on steady-state signals such as vehicle speed and throttle opening for gear shifting, and cannot accurately identify continuous high-load power demands. This causes the vehicle to upshift too early, resulting in insufficient power, or downshift too late, leading to power interruption, which seriously affects driving safety and transportation efficiency. 2. High dependence on and low reliability of external sensors: Existing technologies attempt to use acceleration sensors or slope sensors to assist in identifying road conditions, but the signals from these sensors are easily affected by vehicle vibrations and road bumps, leading to inaccurate slope identification. Incorrect signal input can mislead the transmission control unit (TCU), causing incorrect gear shifts, such as upshifting when high torque is needed for climbing. 3. Lack of consideration for the coupling of critical component states: Current shifting strategies generally fail to coordinate the driver's real-time dynamic intentions with the thermal load status of the drive motor. When the motor temperature is too high, its output torque will be limited. If the system still responds to the driver's strong power request (such as a sudden downshift) according to the conventional logic at this time, it may not be able to achieve the expected results, or even exacerbate the risk of motor overheating and damage vehicle reliability. Summary of the Invention The technical problem solved by this invention is to provide a method and system for compensating shift points of an AMT (Automated Manual Transmission) in electric commercial vehicles, so as to solve the problem that the traditional AMT shift control of electric commercial vehicles is not adaptable to complex working conditions in the prior art.

[0003] The basic solution provided by this invention is: a method for compensating shift points in an AMT (Automated Manual Transmission) system for electric commercial vehicles, comprising: S1: Real-time acquisition of driver intention signals, motor status signals, and vehicle operation signals during vehicle operation; S2: Preprocess the collected driver intention signal, motor status signal, and vehicle operation signal to generate preprocessed driver intention signal, motor status signal, and vehicle operation signal; S3: Preset driver intention intensity coefficient calculation formula. Based on the preprocessed driver intention signal and the preset driver intention intensity coefficient calculation formula, the driver intention intensity coefficient representing the urgency of the current power demand is obtained. S4: Construct a motor temperature influence model, input the preprocessed motor state signal and vehicle operation signal into the motor temperature influence model, and output the motor temperature influence coefficient that characterizes the motor torque output capability; S5: Construct a comprehensive compensation model, input the driver intention intensity coefficient, motor temperature influence coefficient and preprocessed vehicle operation signal into the comprehensive compensation model, and output the comprehensive compensation coefficient; S6: Based on the comprehensive compensation coefficient, the preset standard shift curve is offset in real time to generate dynamic shift points, which are then transmitted to the transmission control unit of the electric commercial vehicle to execute the corresponding shift operation.

[0004] Furthermore, S3 includes: S3-1: Approximate calculation of the rate of change of accelerator pedal opening using the first derivative. The expression is:

[0005] in, This indicates the current accelerator pedal opening value. This represents the accelerator pedal opening value at the previous sampling point. Indicates the sampling time interval; S3-2: Applying a first-order inertial filter to the rate of change of accelerator pedal opening. The low-pass filtering process is expressed as follows:

[0006] in, This represents the rate of change of the accelerator pedal opening at the current moment after filtering. Represents the filter coefficients. This represents the rate of change of the accelerator pedal opening after filtering at the previous moment; S3-3: Result of the filtered accelerator pedal opening change rate Mapped to the driver's intent intensity coefficient.

[0007] Furthermore, the mapping process in S3-3 is specifically as follows: when The value indicates the driver's intention to release the pedal or decelerate; therefore, the driver's intention intensity coefficient is... It is in a conservative mode; when , indicating the intention to accelerate, then the driver's intention intensity coefficient Using a piecewise function, the expression is:

[0008] in, This represents the result of the rate of change of accelerator pedal opening after filtering.

[0009] Furthermore, S4 includes: S4-1: Based on the characteristics of motor temperature and torque decay, construct a model of the influence of motor temperature; S4-2: Input the preprocessed motor status signal and vehicle operation signal into the motor temperature influence model to obtain the motor temperature influence coefficient. The expression is:

[0010] in, Indicates motor temperature. , , Both represent temperature thresholds, and ; S4-3: Construct a temperature influence mapping table based on the motor temperature influence coefficient and motor temperature range to generate a quick query for shift strategy adjustment.

[0011] Furthermore, in S5, a comprehensive compensation model is constructed. The driver's intention intensity coefficient, the motor temperature influence coefficient, and the preprocessed vehicle operation signal are input into the comprehensive compensation model, and the output comprehensive compensation coefficient is as follows: The driver intent intensity coefficient and motor temperature influence coefficient are integrated, and a correction factor is introduced based on the preprocessed vehicle operation signal to optimize the balancing effect. The expression is as follows:

[0012] in, This represents the comprehensive compensation coefficient. The driver's intent intensity coefficient. This represents the temperature influence coefficient of the motor. This represents the torque correction factor. This indicates the real-time torque value of the motor. This indicates the maximum output torque of the motor in the current gear.

[0013] Furthermore, S6 includes: S6-1: Based on comprehensive compensation coefficient The upshift speed threshold of the standard shift curve is dynamically adjusted, and the expression is:

[0014] in, This indicates the speed compensation value at the upshift point. This indicates the vehicle speed threshold for upshifting. This indicates the upshift compensation coefficient; S6-2: Based on comprehensive compensation coefficient The downshift point speed threshold of the standard shift curve is dynamically adjusted, and the expression is:

[0015] in, This indicates the speed compensation value at the downshift point. This indicates the vehicle speed threshold for downshifting. This indicates the downshift compensation coefficient; S6-3: Construct constraints, including upshift speed compensation values. The vehicle speed compensation value is greater than the downshift point. ,and Less than or equal to ; S6-4: Based on S6-1 to S6-3, the dynamic shift points are obtained and input to the transmission control unit, which then executes the corresponding shift operation.

[0016] An AMT (Automated Manual Transmission) shift point compensation system for electric commercial vehicles, applied to the aforementioned AMT shift point compensation method for electric commercial vehicles, includes a signal acquisition module, a preprocessing module, a data processing module, a shift map compensation module, and an execution module, wherein: The signal acquisition module is used to collect driver intention signals, motor status signals, and vehicle operation signals in real time during vehicle operation. The preprocessing module is used to preprocess the collected driver intention signals, motor status signals, and vehicle operation signals to generate preprocessed driver intention signals, motor status signals, and vehicle operation signals. The data processing module is used to connect to the preprocessing module and calculate the driver intention intensity coefficient, motor temperature influence coefficient, and comprehensive compensation coefficient. The shift map compensation module is used to dynamically adjust the standard shift line according to the comprehensive compensation coefficient and generate shift points; The execution module is used to control the transmission control unit to perform gear shifts based on dynamically adjusted shift points.

[0017] The principle and advantages of this invention are as follows: The technical solution of this application realizes intelligent compensation of AMT shift points through multi-dimensional signal fusion and dynamic model decision-making. First, key signals that reflect the driver's operating needs, motor working status, and vehicle driving status are collected in real time and pre-processed to eliminate interference to ensure data reliability. Then, the driver's urgent power demand is quantified by a preset formula, and the motor's current torque output capability is judged by relying on the motor temperature influence model and combining the motor's own status and vehicle operating information. Then, through a comprehensive compensation model, the intensity of the driver's power demand, the motor's torque output capability, and the vehicle's real-time operating status are deeply coupled to calculate a comprehensive compensation coefficient that can balance demand and capability. Finally, the fixed standard shift curve is dynamically adjusted according to this coefficient to generate a shift point adapted to the current operating conditions and transmit it to the transmission control unit to realize on-demand shift control.

[0018] Its advantages are: it effectively solves the problem of insufficient adaptability of traditional AMT shift control to complex operating conditions. By accurately capturing the driver's real power demand and dynamically adjusting the shift strategy in combination with the motor status, it can maintain the appropriate gear to ensure continuous torque output and avoid insufficient or interrupted power when strong power is required. At the same time, it can reasonably constrain the shift compensation range in scenarios where the motor status is limited to prevent motor overload damage. At the same time, it does not rely on external sensors that are susceptible to interference, but only makes decisions based on the vehicle's inherent signals, which significantly improves the reliability and stability of shift control. Moreover, the dynamically adjusted shift logic can adapt to different driving scenarios, taking into account both driving power and vehicle component protection, and optimizing the overall driving experience and system durability. Attached Figure Description

[0019] Figure 1 This is a flowchart of an embodiment of the present invention; Figure 2 This is a functional block diagram of an embodiment of the present invention. Detailed Implementation

[0020] The following detailed description illustrates the specific implementation method: The basic implementation examples are as follows: Figure 1 As shown: A method for compensating shift points in an AMT (Automated Manual Transmission) system for electric commercial vehicles, comprising: S1: Real-time acquisition of driver intention signals, motor status signals, and vehicle operation signals during vehicle operation; In this embodiment, a high-precision Hall sensor is used to collect throttle data to obtain the driver's intention signal, a motor temperature sensor collects the motor status signal, and the TCU directly reads and obtains the vehicle operation signal, including but not limited to vehicle speed signal, throttle pedal opening signal, and current gear signal.

[0021] S2: Preprocess the collected driver intention signal, motor status signal, and vehicle operation signal to generate preprocessed driver intention signal, motor status signal, and vehicle operation signal; In this embodiment, the preprocessing includes signal filtering, which removes high-frequency noise from the throttle change rate and vehicle speed signals by using a moving average filter, thus providing high-quality signal data.

[0022] S3: A preset driver intention intensity coefficient calculation formula is used to obtain a driver intention intensity coefficient that characterizes the urgency of the current power demand, based on the preprocessed driver intention signal and the preset driver intention intensity coefficient calculation formula; wherein, S3 includes: S3-1: Approximate calculation of the rate of change of accelerator pedal opening using the first derivative. The expression is:

[0023] in, This represents the current accelerator pedal opening value, normalized to the range of 0-1. This represents the accelerator pedal opening value at the previous sampling point. In this embodiment, the sampling time interval is indicated. Second; S3-2: Applying a first-order inertial filter to the rate of change of accelerator pedal opening. The low-pass filtering process is expressed as follows:

[0024] In this embodiment, low-pass filtering can avoid the influence of noise, wherein, This represents the rate of change of the accelerator pedal opening at the current moment after filtering. This represents the filter coefficient, which is 0.2 in this embodiment, used to smooth instantaneous fluctuations. This represents the rate of change of the accelerator pedal opening after filtering at the previous moment; S3-3: Result of the filtered accelerator pedal opening change rate The mapping to the driver's intent intensity coefficient is as follows: when The value indicates the driver's intention to release the pedal or decelerate; therefore, the driver's intention intensity coefficient is... It is in a conservative mode; when , indicating the intention to accelerate, then the driver's intention intensity coefficient Using a piecewise function, the expression is:

[0025] in, The result represents the rate of change of the accelerator pedal opening after filtering. In this embodiment, the upper limit of the intention intensity coefficient is 1.5, which can prevent overly aggressive shifting.

[0026] S4: Construct a motor temperature influence model. Input the preprocessed motor state signal and vehicle operation signal into the motor temperature influence model, and output the motor temperature influence coefficient characterizing the motor torque output capability; wherein, S4 includes: S4-1: Based on the characteristics of motor temperature and torque decay, construct a model of the influence of motor temperature; S4-2: Input the preprocessed motor status signal and vehicle operation signal into the motor temperature influence model to obtain the motor temperature influence coefficient. The expression is:

[0027] in, Indicates motor temperature. , , Both represent temperature thresholds, and In this embodiment, , , .

[0028] S4-3: Construct a temperature influence mapping table based on the motor temperature influence coefficient and the motor temperature range to generate a quick query for shift strategy adjustment; in this embodiment, it is shown in Table 1 below: Table 1. Temperature Effect Mapping Table

[0029] Therefore, the constructed temperature influence mapping table can be used to simplify the continuous calculation of the temperature influence coefficient and facilitate quick lookup.

[0030] S5: Construct a comprehensive compensation model, inputting the driver intention intensity coefficient, motor temperature influence coefficient, and preprocessed vehicle operation signal into the comprehensive compensation model, and outputting the comprehensive compensation coefficient; specifically: The driver intent intensity coefficient and motor temperature influence coefficient are integrated, and a correction factor is introduced based on the preprocessed vehicle operation signal to optimize the balancing effect. The expression is as follows:

[0031] in, This represents the comprehensive compensation coefficient. The driver's intent intensity coefficient. This represents the temperature influence coefficient of the motor. This represents the torque correction factor. This indicates the real-time torque value of the motor. This indicates the maximum output torque of the motor in the current gear.

[0032] In this embodiment, the driver's intention and the motor's capability are integrated, and a dynamic weighted multiplicative model is adopted, introducing a correction factor to optimize the balance effect. The correction factor... When the actual output torque of the motor is close to its maximum value, the compensation range is appropriately increased to match the heavy load requirements; and constraints are set. To avoid overcompensation or undercompensation.

[0033] S6: Based on a comprehensive compensation coefficient, real-time offset compensation is performed on the preset standard shift curve to generate dynamic shift points, which are then transmitted to the transmission control unit of the electric commercial vehicle to execute the corresponding shift operation. S6 includes: S6-1: Based on comprehensive compensation coefficient The upshift speed threshold of the standard shift curve is dynamically adjusted, and the expression is:

[0034] in, This indicates the speed compensation value at the upshift point. This indicates the vehicle speed threshold for upshifting. This indicates the upshift compensation coefficient; the value is 0.25 for gears 1-3 and 0.15 for gears 4-6.

[0035] S6-2: Based on comprehensive compensation coefficient The downshift point speed threshold of the standard shift curve is dynamically adjusted, and the expression is:

[0036] in, This indicates the speed compensation value at the downshift point. This indicates the vehicle speed threshold for downshifting. This represents the downshift compensation factor; 0.15 for gears 1-3, and 0.20 for gears 4-6. S6-3: Construct constraints, including upshift speed compensation values. The vehicle speed compensation value is greater than the downshift point. ,and Less than or equal to Avoid gear shift conflicts.

[0037] S6-4: Based on S6-1 to S6-3, the dynamic shift points are obtained and input to the transmission control unit, which then executes the corresponding shift operation.

[0038] like Figure 2As shown, in another embodiment of this example, an electric commercial vehicle AMT shift point compensation system is also included, applied to the above-described electric commercial vehicle AMT shift point compensation method, comprising a signal acquisition module, a preprocessing module, a data processing module, a shift map compensation module, and an execution module, wherein: The signal acquisition module is used to collect driver intention signals, motor status signals, and vehicle operation signals in real time during vehicle operation. The preprocessing module is used to preprocess the collected driver intention signals, motor status signals, and vehicle operation signals to generate preprocessed driver intention signals, motor status signals, and vehicle operation signals. The data processing module is used to connect to the preprocessing module and calculate the driver intention intensity coefficient, motor temperature influence coefficient, and comprehensive compensation coefficient. The shift map compensation module is used to dynamically adjust the standard shift line according to the comprehensive compensation coefficient and generate shift points; The execution module is used to control the transmission control unit to perform gear shifts based on dynamically adjusted shift points.

[0039] Example 2: The difference between Example 2 and Example 3 is that, for the calculation of the driver intention intensity coefficient in S3, this application also considers calculating the driver intention intensity coefficient based on the throttle change rate, throttle opening, and duration. Specifically, S3 includes: S3-4: Extract and calculate the normalization function of the throttle change rate in the preprocessed driver intention signal, and use a Sigmoid curve to enhance robustness. The expression is:

[0040] in, Let be the normalized function of the rate of change of throttle. Indicates the rate of change of throttle; This represents the slope coefficient of the curve. The threshold for the critical rate of change of throttle; In this embodiment, it is 0.05. ,when hour, ; S3-5: Extract and calculate the throttle opening normalization function from the preprocessed driver intention signal. The calculation uses a piecewise linear model, and the expression is:

[0041] in, This represents the normalized function of throttle opening. Indicates throttle opening; S3-6: Extract and calculate the throttle duration weighted function value from the preprocessed driver intention signal. The expression is:

[0042] in, This represents the weighted function value for throttle duration. This indicates the duration when the throttle opening is greater than a preset value; in this embodiment, the preset value is 60. , and when hour, This reflects the need for continuous heavy loads; S3-7: Calculate the driver intent intensity coefficient based on the normalized function of throttle change rate, the normalized function of throttle opening, and the weighted function value of throttle duration. The expression is as follows:

[0043] in, Indicates instantaneous demand weight. Indicates the steady-state demand weight. This represents the weight of persistent demand; in this embodiment, , , .

[0044] To better illustrate the above technical solution, a real-world scenario is constructed for detailed explanation: an electric heavy truck is driving on a slope, and the driver presses the accelerator pedal deeply to accelerate. Initial state: The electric heavy-duty truck is equipped with a 6-speed AMT, currently in 3rd gear, and the vehicle speed is 35 km / h. Motor temperature Throttle opening Duration ; Signal processing: According to The numerical value is used to calculate the intention intensity coefficient. According to the motor temperature influence model, because ,because Therefore, the motor temperature influence coefficient , , Then the comprehensive compensation coefficient .

[0045] Shift point compensation: Standard upshift point , ,but ; Standard downshift point , ,but .

[0046] Execution result: The vehicle reached a speed of Without shifting up, continue to output high torque in 3rd gear until the vehicle speed reaches [speed value missing]. Alternatively, the driver can release the accelerator to ensure sufficient power for climbing.

[0047] The above are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. An electric commercial vehicle AMT shift point compensation method, characterized by: The method comprises the following steps: S1: collecting driver intention signals, motor state signals and vehicle running signals in real time during vehicle operation; S2: preprocessing the collected driver intention signals, motor state signals and vehicle running signals to generate preprocessed driver intention signals, motor state signals and vehicle running signals; S3: presetting a driver intention intensity coefficient calculation formula, and obtaining a driver intention intensity coefficient representing the urgency of current power demand based on the preprocessed driver intention signals and the preset driver intention intensity coefficient calculation formula; S4: constructing a motor temperature influence model, inputting the preprocessed motor state signals and vehicle running signals into the motor temperature influence model, and outputting a motor temperature influence coefficient representing the motor torque output capability; S5: constructing a comprehensive compensation model, inputting the driver intention intensity coefficient, the motor temperature influence coefficient and the preprocessed vehicle running signals into the comprehensive compensation model, and outputting a comprehensive compensation coefficient; S6: performing real-time offset compensation on the preset standard shift curve based on the comprehensive compensation coefficient, generating a dynamic shift point, and transmitting the dynamic shift point to a gearbox control unit of the electric commercial vehicle to perform corresponding shift operation.

2. The AMT shift point compensation method for electric commercial vehicles according to claim 1, characterized in that: The S3 comprises: S3-1: Calculate the accelerator pedal opening rate of change using a first derivative approximation , the expression is: wherein, represents a current accelerator pedal opening value, represents a previous sample point accelerator pedal opening value, represents a sampling time interval; S3-2: First order inertial filter on throttle pedal opening rate of change Low pass filter, expression: wherein, represents a result of the filtered change rate of the accelerator pedal opening degree at the current time point; represents a filter coefficient, represents a result of the filtered change rate of the accelerator pedal opening degree at the previous time point; S3-3: Filtered throttle pedal opening rate result mapped to the driver intent intensity coefficient.

3. The AMT shift point compensation method for electric commercial vehicles according to claim 2, characterized in that: The mapping process in S3-3 is specifically: When , indicating a pedal release or deceleration intention, the driver intention intensity coefficient , is in a conservative mode; When , indicates the acceleration intention, then the driver intention intensity coefficient is expressed by a piecewise function, and the expression is: wherein, represents the filtered throttle pedal opening rate result.

4. The AMT shift point compensation method for electric commercial vehicles according to claim 3, characterized in that: The S4 comprises: S4-1: constructing a motor temperature influence model based on motor temperature and torque attenuation characteristics; S4-2: input the pretreated motor state signal and vehicle operation signal into the motor temperature influence model to obtain a motor temperature influence coefficient , the expression is: wherein, represents a motor temperature, , , all represent temperature thresholds, and ; S4-3: constructing a temperature influence mapping table based on the motor temperature influence coefficient and the motor temperature range to generate a shift strategy adjustment quick query.

5. The electric commercial vehicle AMT shift point compensation method of claim 4, wherein: In the S5, the driver intention intensity coefficient, the motor temperature influence coefficient and the preprocessed vehicle running signals are input into the comprehensive compensation model to output the comprehensive compensation coefficient, which is specifically: The driver intention intensity coefficient and the motor temperature influence coefficient are fused, and a correction factor is introduced based on the preprocessed vehicle running signals to optimize the balance effect, and the expression is: wherein, represents a comprehensive compensation coefficient, is a driver intention intensity coefficient, represents a motor temperature influence coefficient, represents a torque correction coefficient, represents a motor real-time torque value, represents a maximum output torque of the motor at the current gear.

6. The electric commercial vehicle AMT shift point compensation method of claim 5, wherein: The S6 comprises: S6-1: Based on the comprehensive compensation coefficient The upshift point vehicle speed threshold of the standard shift curve is dynamically adjusted, and the expression is: wherein, represents an upshift point vehicle speed compensation value, represents an upshift point vehicle speed threshold value, represents an upshift compensation coefficient; S6-2: Based on the comprehensive compensation coefficient The downshift point vehicle speed threshold of the standard shift curve is dynamically adjusted, and the expression is: wherein, represents a downshift point vehicle speed compensation value, represents a downshift point vehicle speed threshold value, represents a downshift compensation coefficient; S6-3: constructing a constraint condition including an upshift point vehicle speed compensation value greater than a downshift point vehicle speed compensation value , and less than or equal to ; S6-4: obtaining the dynamic shift point based on S6-1 to S6-3, inputting the dynamic shift point into the gearbox control unit, and performing corresponding shift operation by the gearbox control unit.

7. An electric commercial vehicle AMT shift point compensation system applied to an electric commercial vehicle AMT shift point compensation method according to any one of claims 1-6, characterized in that: The method comprises a signal acquisition module, a preprocessing module, a data processing module, a shift map compensation module and an execution module, wherein: The signal acquisition module is used to collect driver intention signals, motor state signals and vehicle running signals in real time during vehicle operation; The preprocessing module is used to preprocess the collected driver intention signals, motor state signals and vehicle running signals to generate preprocessed driver intention signals, motor state signals and vehicle running signals; The data processing module is used to connect the preprocessing module and calculate the driver intention intensity coefficient, the motor temperature influence coefficient and the comprehensive compensation coefficient; The shift map compensation module is used to dynamically adjust the standard shift line according to the comprehensive compensation coefficient to generate a shift point; The execution module is used to control the gearbox control unit to perform shift based on the dynamically adjusted shift point.

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