A method and system for adaptively adjusting energy management parameters of solid rockets
By online correction of the energy management parameters and final working timing of solid rockets, the problem of insufficient adaptability of solid rockets when load mass changes is solved, improving orbital accuracy and reducing fuel consumption.
Patent Information
- Application Number
- CN202411834546.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-12
- Publication Date
- 2025-04-04
AI Technical Summary
When the load mass changes in existing solid rockets, energy management parameters need to be redesigned, and they are not adaptable to load mass deviation, which affects the orbital accuracy and fuel consumption of the final propulsion system.
By determining the reserved speed of the final speed correction section under nominal operating conditions and the alternating posture angle of the energy management section, and correcting these parameters online according to the real-time velocity increment, adjusting the last stage of the rocket to enable the final stage propulsion system, and achieving adaptive adjustment of load mass deviation.
It improves the rocket's adaptability to load mass deviation, improves the orbital accuracy under extreme operating conditions, and reduces fuel consumption of the final propulsion system.
Smart Images
Figure CN119756089A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of rockets, and in particular, to a method and system for adaptively adjusting energy management parameters of solid rockets. Background Art
[0002] In order to increase the carrying capacity and reduce the difficulty of system design, solid-propellant launch vehicles often adopt an exhaustion shutdown strategy based on alternating attitude energy management. In order to improve the accuracy of orbital insertion, the rocket is in an under-energy state when it is exhausted, and then the terminal repair propulsion system is used to accurately control the orbital parameters of the rocket. The energy management parameters are generally designed according to the nominal operating conditions so that the rocket is in a set under-energy state when the main engine is exhausted. However, when the payload mass changes, the energy management parameters often need to be redesigned, and the above strategy is not adaptable enough to the deviation state of the rocket. If the rocket speed is too high when the main engine is exhausted, the orbital insertion accuracy will deteriorate. On the contrary, if the rocket speed is too low when the main engine is exhausted, it will consume more fuel of the terminal repair propulsion system.
[0003] Therefore, how to provide a method for adaptively adjusting energy management parameters to improve the rocket's adaptability to payload mass deviation has become an urgent problem to be solved in this field. Summary of the invention
[0004] In order to solve the above problems, the present application proposes a method for adaptively adjusting the energy management parameters of a solid rocket, comprising the following steps: determining the reserved speed of the terminal speed correction section and the alternating attitude adjustment angle of the energy management section under nominal conditions; after completing the determination of the reserved speed of the terminal speed correction section and the alternating attitude adjustment angle of the energy management section under nominal conditions, determining the apparent speed increment of the terminal correction propulsion system within the specified working time at the start of the rocket's final stage; setting the reserved speed coefficient of the terminal speed correction section, the reserved speed of the terminal speed correction section, the alternating attitude adjustment angle of the energy management section, and the apparent speed increment generated by turning on the terminal correction propulsion system within a fixed time before the start of the final stage under nominal conditions as various elements; after setting the various elements, setting the flight timing of the final stage, turning on the terminal correction propulsion system before the ignition of the main engine of the final stage, and determining the real-time apparent speed increment of the rocket generated within a fixed time; and correcting the reserved speed coefficient of the terminal speed correction section and the alternating attitude adjustment angle of the energy management section online according to the determined real-time apparent speed increment of the rocket and various elements.
[0005] The method for adaptively adjusting the energy management parameters of a solid rocket as described above, wherein the reserved speed ΔV of the terminal speed correction section under the nominal working condition is calculated based on the parameters of the final stage engine and the nominal trajectory parameters. std Alternating attitude adjustment angles in the energy management section Specifically expressed as:
[0006] ΔV std =K m W m
[0007]
[0008] Where K m The speed coefficient reserved for the final speed correction section, W m is the final apparent velocity increment under nominal conditions, and F represents the function.
[0009] The above-mentioned method for adaptively adjusting the energy management parameters of solid rockets, wherein the apparent velocity increment ΔW of the last repair propulsion system working within the ΔT1 time at the start time of the rocket last stage is calculated according to the nominal conditions. std , specifically expressed as:
[0010]
[0011] Where P is the thrust of the last propulsion system when it is working, M m is the mass of the rocket's final stage at the start of its run.
[0012] The method for adaptively adjusting the energy management parameters of solid rockets as described above, before determining the real-time apparent velocity increment of the rocket, also includes adjusting the flight timing of the rocket's last stage, turning on the last repair propulsion system before the ignition of the last stage main engine, and setting the turn-on time period to ΔT1.
[0013] The solid rocket energy management parameter adaptive adjustment method as described above, wherein the rocket real-time apparent velocity increment ΔW within ΔT1 is determined online , specifically expressed as:
[0014]
[0015] Where N1 = ΔT1 / T s , T s is the navigation solution period, δW i is the axial apparent velocity increment calculated during the navigation cycle i.
[0016] A solid rocket energy management parameter adaptive adjustment system specifically comprises: a reserved speed and alternating attitude adjustment angle determination unit, an apparent speed increment determination unit, a parameter setting unit, a real-time apparent speed increment determination unit and an online correction unit; the reserved speed and alternating attitude adjustment angle determination unit is used to determine the reserved speed of the terminal speed correction section and the alternating attitude adjustment angle of the energy management section under nominal working conditions; the apparent speed increment determination unit is used to determine the apparent speed increment of the terminal repair propulsion system within a specified working time at the start of the rocket's final stage; the parameter setting unit is used to use the reserved speed coefficient of the terminal speed correction section, the reserved speed of the terminal speed correction section, the alternating attitude adjustment angle of the energy management section and the apparent speed increment generated by turning on the terminal repair propulsion system within a fixed time before the start of the final stage under nominal working conditions as parameters; the real-time apparent speed increment determination unit is used to set the final stage flight sequence, turn on the final repair propulsion system before the final stage main engine is ignited, and determine the rocket's real-time apparent speed increment generated within a fixed time; the online correction unit is used to correct the reserved speed coefficient of the terminal speed correction section and the alternating attitude adjustment angle of the energy management section online according to the determined real-time apparent speed increment of the rocket and the parameters.
[0017] In the above-mentioned solid rocket energy management parameter adaptive adjustment system, the reserved speed and alternating attitude adjustment angle determination unit calculates the reserved speed ΔV of the terminal speed correction section under the nominal working condition based on the final stage engine parameters and the nominal trajectory parameters. std Alternating attitude adjustment angles in the energy management section Specifically expressed as:
[0018] ΔV std =K m W m
[0019]
[0020] Where K m The speed coefficient reserved for the final speed correction section, W m is the final apparent velocity increment under nominal conditions, and F represents the function.
[0021] In the above-mentioned solid rocket energy management parameter adaptive adjustment system, the apparent velocity increment determination unit calculates the apparent velocity increment ΔW of the last repair propulsion system working within the ΔT1 time at the start time of the rocket last stage according to the nominal conditions. std , specifically expressed as:
[0022]
[0023] Where P is the thrust of the last propulsion system when it is working, M m is the mass of the rocket's final stage at the start of its run.
[0024] In the solid rocket energy management parameter adaptive adjustment system as described above, the real-time apparent velocity increment determination unit determines the real-time apparent velocity increment of the rocket and further includes adjusting the flight timing of the rocket's last stage, turning on the last repair propulsion system before the last stage main engine is ignited, and setting the turn-on time period to ΔT1.
[0025] In the above-mentioned solid rocket energy management parameter adaptive adjustment system, the real-time apparent velocity increment determination unit determines the rocket real-time apparent velocity increment ΔW within ΔT1. online , specifically expressed as:
[0026]
[0027] Where N1 = ΔT1 / T s , T s is the navigation solution period, δW i is the axial apparent velocity increment calculated during the navigation cycle i.
[0028] This application has the following beneficial effects:
[0029] This application adjusts the working timing of the rocket's last stage, evaluates the rocket's current state according to real-time flight parameters, and then selects different energy management parameters according to the state parameter range, thereby adjusting the dissipated energy and the maximum attitude adjustment angle of energy management. It can improve the rocket's adaptability to payload mass deviations, improve orbital accuracy under extreme working conditions, and reduce fuel consumption of the terminal propulsion system. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.
[0031] Figure 1 is a flow chart of a method for adaptively adjusting energy management parameters of a solid rocket provided in an embodiment of the present application;
[0032] Figure 2 It is a schematic diagram of the internal structure of a solid rocket energy management parameter adaptive adjustment system provided according to an embodiment of the present application. DETAILED DESCRIPTION
[0033] The following is a clear and complete description of the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.
[0034] This application uses an online estimation method to evaluate the rocket state, and then adaptively selects energy management parameters based on the rocket state, and then adjusts the rocket state when the main engine is exhausted to expand the rocket's adaptability to payload mass deviations to ensure the rocket's orbital accuracy and low fuel consumption of the terminal propulsion system.
[0035] Embodiment 1
[0036] Based on the alternating attitude energy management method, this embodiment adjusts the working timing of the rocket's final stage, evaluates the system's flight status online, and determines the energy management parameters (including the reserved speed of the terminal speed correction section and the alternating attitude adjustment angle of the energy management section) according to the flight status to achieve self-adaptation to the payload mass deviation.
[0037] like Figure 1 As shown, the solid rocket energy management parameter adaptive adjustment method provided in this embodiment specifically includes the following steps:
[0038] Step S110: Determine the reserved speed of the terminal speed correction section and the alternating attitude adjustment angle of the energy management section under the nominal working condition.
[0039] In this embodiment, the terminal speed correction section reserved speed ΔV under the nominal working condition is calculated based on the final stage engine parameters and the nominal trajectory parameters. std Alternating attitude adjustment angles in the energy management section Specifically expressed as:
[0040] ΔV std =K m W m
[0041]
[0042] Where K m The speed coefficient reserved for the final speed correction section, W m is the final apparent velocity increment under nominal conditions, F represents the function, =ΔV std and W m function.
[0043] Step S120: After completing the determination of the reserved speed of the terminal speed correction section and the alternating attitude adjustment angle of the energy management section under the nominal working conditions, determine the apparent speed increment within the specified time when the terminal correction propulsion system is working (the main engine is not working) at the beginning of the rocket's final stage.
[0044] The apparent velocity increment ΔW within a period of ΔT1 (e.g. 5s) when the last stage of the rocket starts to work is calculated according to the nominal conditions. std , specifically expressed as:
[0045]
[0046] Where P is the thrust of the last propulsion system when it is working, M m is the mass of the rocket's final stage at the start of its run.
[0047] Step S130: The reserved speed coefficient of the terminal speed correction stage, the reserved speed of the terminal speed correction stage, the alternating attitude adjustment angle of the energy management stage, and the apparent speed increment generated by starting the terminal correction propulsion system within a fixed time before the start of the terminal stage under nominal working conditions are set as various parameters.
[0048] The parameter ΔV is calculated based on the nominal conditions. std , ΔW std And the reserved speed coefficient K of the final speed correction section m As elements.
[0049] Step S140: After setting all parameters, set the final stage flight sequence, start the final stage propulsion system before the final stage main engine is ignited, and calculate the real-time apparent velocity increment of the rocket generated within the specified time.
[0050] The flight sequence of the final stage of the rocket is adjusted, and the final repair propulsion system is turned on before the ignition of the final stage main engine. Assuming the start time period is ΔT1, the real-time apparent velocity increment ΔW of the rocket within ΔT1 is calculated using the axial apparent velocity calculated by navigation. online , specifically expressed as:
[0051]
[0052] Where N1 = ΔT1 / T s , T s is the navigation solution period, δW i It is the axial velocity increment calculated by navigation in the i-th cycle.
[0053] Step S150: based on the determined real-time apparent velocity increment and various parameters of the arrow, the reserved velocity coefficient of the terminal velocity correction stage and the alternating attitude adjustment angle of the energy management stage are corrected online.
[0054] The reserved speed coefficient of the terminal speed correction phase and the alternating attitude adjustment angle of the energy management phase in the online correction are specifically expressed as follows:
[0055]
[0056] ΔV′=K′ m W m -ΔW online
[0057]
[0058] where K′ m Reserve speed coefficient for online final speed correction stage, K ml ,K mu K′ m The lower and upper limits of ΔV′ are the reserved speed for the online final speed correction section. It is used to correct the alternating attitude adjustment angle in the energy management section online.
[0059] Embodiment 2
[0060] like Figure 2 As shown, this embodiment provides a solid rocket energy management parameter adaptive adjustment system, which specifically includes: a reserved speed and alternating attitude adjustment angle determination unit 210, an apparent speed increment determination unit 220, a parameter setting unit 230, a real-time apparent speed increment determination unit 240 and an online correction unit 250.
[0061] The reserved speed and alternating attitude adjustment angle determination unit 210 is used to determine the reserved speed of the terminal speed correction section and the alternating attitude adjustment angle of the energy management section under the nominal working condition.
[0062] In this embodiment, the terminal speed correction section reserved speed ΔV under the nominal working condition is calculated based on the final stage engine parameters and the nominal trajectory parameters. std Alternating attitude adjustment angles in the energy management section Specifically expressed as:
[0063] ΔV std =K m W m
[0064]
[0065] Where K m Reserve speed coefficient for final speed correction section, W m is the final apparent velocity increment under nominal conditions, F represents the function, =ΔV std and W m function.
[0066] The apparent velocity increment determination unit 220 is used to determine the apparent velocity increment within the specified working time of the terminal correction propulsion system at the start time of the rocket's last stage after completing the determination of the reserved speed of the terminal speed correction section and the alternating attitude adjustment angle of the energy management section under the nominal working conditions.
[0067] The apparent velocity increment ΔW within a period of ΔT1 (e.g. 5s) when the last stage of the rocket starts to work is calculated according to the nominal conditions. std , specifically expressed as:
[0068]
[0069] Where P is the thrust of the last propulsion system when it is working, M m is the mass of the rocket's final stage at the start of its run.
[0070] The parameter setting unit 230 is used to take the reserved speed coefficient of the terminal speed correction stage, the reserved speed of the terminal speed correction stage, the alternating attitude adjustment angle of the energy management stage, and the apparent speed increment generated by starting the terminal correction propulsion system within a fixed time before the start of the terminal stage under nominal working conditions as parameters.
[0071] The parameter ΔV is calculated based on the nominal conditions. std , ΔW std And the reserved speed coefficient K of the final speed correction section m As elements.
[0072] The real-time apparent velocity increment determination unit 240 is used to set the final stage flight sequence, start the final repair propulsion system before the final stage main engine ignites, and determine the real-time apparent velocity increment of the rocket generated within a fixed time.
[0073] The flight sequence of the final stage of the rocket is adjusted, and the final repair propulsion system is turned on before the ignition of the final stage main engine. Assuming the start time period is ΔT1, the real-time apparent velocity increment ΔW of the rocket within ΔT1 is calculated using the axial apparent velocity calculated by navigation. online , specifically expressed as:
[0074]
[0075] Where N1 = ΔT1 / T s , T s is the navigation solution period, δW i is the axial apparent velocity increment calculated during the navigation cycle i.
[0076] The online correction unit 250 is used to correct the reserved speed coefficient of the terminal speed correction stage and the alternating attitude adjustment angle of the energy management stage online according to the determined real-time apparent speed increment and various parameters of the rocket.
[0077] The reserved speed coefficient of the terminal speed correction phase and the alternating attitude adjustment angle of the energy management phase in the online correction are specifically expressed as follows:
[0078]
[0079] ΔV′=K′ m W m -ΔW online
[0080]
[0081] where K′ m Reserve speed coefficient for online final speed correction stage, K ml ,K mu K′ m The lower and upper limits of ΔV′ are the reserved speed for the online final speed correction section. It is used to correct the alternating attitude adjustment angle in the energy management section online.
[0082] The present application also provides a computer storage medium, which stores computer instructions. When the computer instructions are called, they are used to execute the solid rocket energy management parameter adaptive adjustment method.
[0083] The embodiments disclosed in the present application provide a computer-readable storage medium, in which computer program instructions are stored. When the computer program instructions are executed on a computer, the computer executes the above-mentioned method for adaptively adjusting energy management parameters of a solid rocket.
[0084] An embodiment of the present application provides a processor for processing the above-mentioned method for adaptively adjusting energy management parameters of a solid rocket.
[0085] In the embodiment of the present application, the processor may be an integrated circuit chip having the ability to process signals. The processor may be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.
[0086] The methods, steps and logic block diagrams disclosed in the embodiments of the present invention can be implemented or executed. The general processor can be a microprocessor or the processor can also be any conventional processor, etc. The steps of the method disclosed in the embodiments of the present invention can be directly embodied as a hardware decoding processor for execution, or can be executed by a combination of hardware and software modules in the decoding processor. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The processor reads the information in the storage medium and completes the steps of the above method in combination with its hardware.
[0087] The storage medium may be a memory, which may be, for example, a volatile memory or a nonvolatile memory, or may include both volatile and nonvolatile memory.
[0088] Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory can be a random access memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM) and direct RAM bus random access memory (DRRAM).
[0089] This application has the following beneficial effects:
[0090] This application adjusts the working timing of the rocket's last stage, evaluates the rocket's current state according to real-time flight parameters, and then selects different energy management parameters according to the state parameter range, thereby adjusting the dissipated energy and the maximum attitude adjustment angle of energy management. It can improve the rocket's adaptability to payload mass deviations, improve orbital accuracy under extreme working conditions, and reduce fuel consumption of the terminal propulsion system.
[0091] Although the present application is described with reference to examples, this is for illustrative purposes only and is not intended to limit the present application, and changes, additions and / or deletions to the embodiments may be made without departing from the scope of the present application.
[0092] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.
Claims
1. A method for adaptively adjusting energy management parameters of a solid rocket, characterized in that: The following steps are involved: Determine the reserved speed in the terminal speed correction section and the alternating attitude adjustment angle in the energy management section under nominal working conditions; After completing the determination of the reserved speed of the terminal speed correction phase and the alternating attitude adjustment angle of the energy management phase under the nominal working condition, determine the apparent speed increment within the specified working time of the terminal correction propulsion system at the start time of the rocket's final stage; The reserved speed coefficient of the terminal speed correction phase, the reserved speed of the terminal speed correction phase, the alternating attitude adjustment angle of the energy management phase, and the apparent speed increment generated by turning on the terminal correction propulsion system within a fixed time before the start of the terminal stage under nominal working conditions are set as various parameters; After setting all the parameters, set the final stage flight sequence, start the final repair propulsion system before the final stage main engine ignites, and determine the real-time apparent velocity increment of the rocket generated within a fixed time; According to the determined real-time apparent velocity increment and other parameters of the arrow, the reserved velocity coefficient of the terminal velocity correction stage and the alternating attitude adjustment angle of the energy management stage are corrected online.
2. The method for adaptively adjusting the energy management parameters of a solid rocket according to claim 1, characterized in that: Calculate the reserved speed ΔV of the terminal speed correction section under nominal working conditions based on the final stage engine parameters and nominal trajectory parameters std Alternating attitude adjustment angles in the energy management section Specifically expressed as: ΔV std =K m W m Where K m Reserve speed coefficient for final speed correction section, W m is the final apparent velocity increment under nominal conditions, and F represents the function.
3. The method for adaptively adjusting the energy management parameters of a solid rocket according to claim 1, characterized in that: The apparent velocity increment ΔW during the ΔT1 time of the final repair propulsion system at the start of the rocket's final stage is calculated according to the nominal conditions. std , specifically expressed as: Where P is the thrust of the last propulsion system when it is working, M m is the mass of the rocket's final stage at the start of its run.
4. The method for adaptively adjusting the energy management parameters of a solid rocket according to claim 1, characterized in that: Before determining the real-time apparent velocity increment of the rocket, it also includes adjusting the flight timing of the rocket's final stage, turning on the final repair propulsion system before the final stage main engine ignites, and setting the turn-on time period to ΔT1.
5. The method for adaptively adjusting the energy management parameters of a solid rocket as claimed in claim 4, characterized in that: Determine the rocket's real-time apparent velocity increment ΔW within ΔT1 online , specifically expressed as: Where N1 = ΔT1 / T s , T s is the navigation solution period, δW i is the axial apparent velocity increment calculated during the navigation cycle i.
6. A solid rocket energy management parameter adaptive adjustment system, characterized in that: Specifically include: A reserved speed and alternating attitude adjustment angle determination unit, an apparent speed increment determination unit, a parameter setting unit, a real-time apparent speed increment determination unit, and an online correction unit; A reserved speed and alternating attitude adjustment angle determination unit is used to determine the reserved speed of the terminal speed correction section and the alternating attitude adjustment angle of the energy management section under nominal working conditions; An apparent velocity increment determination unit is used to determine the apparent velocity increment within a specified time of operation of the final repair propulsion system at the start time of the final stage of the rocket; A parameter setting unit is used to use the reserved speed coefficient of the terminal speed correction stage, the reserved speed of the terminal speed correction stage, the alternating attitude adjustment angle of the energy management stage, and the apparent speed increment generated by starting the terminal correction propulsion system within a fixed time before the start of the terminal stage under nominal working conditions as parameters; The real-time apparent velocity increment determination unit is used to set the final stage flight sequence, start the final repair propulsion system before the final stage main engine ignites, and determine the real-time apparent velocity increment of the rocket generated within a fixed time; The online correction unit is used to correct the reserved speed coefficient of the terminal speed correction stage and the alternating attitude adjustment angle of the energy management stage online according to the determined real-time apparent speed increment and other parameters of the rocket.
7. The solid rocket energy management parameter adaptive adjustment system according to claim 6, characterized in that: The reserved speed and alternating attitude angle determination unit calculates the reserved speed ΔV of the terminal speed correction section under the nominal working condition based on the final stage engine parameters and the nominal trajectory parameters. std Alternating attitude adjustment angles in the energy management section Specifically expressed as: ΔV std =K m W m Where K m Reserve speed coefficient for final speed correction section, W m is the final apparent velocity increment under nominal conditions, and F represents the function.
8. The solid rocket energy management parameter adaptive adjustment system according to claim 6, characterized in that: The apparent velocity increment determination unit calculates the apparent velocity increment ΔW within the ΔT1 time of the last stage of the rocket starting time according to the nominal conditions. std , specifically expressed as: Where P is the thrust of the last propulsion system when it is working, M m is the mass of the rocket's final stage at the start of its run.
9. The solid rocket energy management parameter adaptive adjustment system according to claim 6, characterized in that: The real-time apparent velocity increment determination unit determines the real-time apparent velocity increment of the rocket, including adjusting the flight timing of the rocket's final stage, starting the final repair propulsion system before the final stage main engine ignites, and setting the start time period to ΔT1.
10. The solid rocket energy management parameter adaptive adjustment system according to claim 9, characterized in that: The real-time apparent velocity increment determination unit determines the rocket real-time apparent velocity increment ΔW within ΔT2 online , specifically expressed as: Where N1 = ΔT1 / T s , T s is the navigation solution period, δW i is the axial apparent velocity increment calculated during the navigation cycle i.