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Study on passive momentum exchange landing gear using two-dimensional analysis
Abstract
This paper discusses a landing response control system based on the momentum exchange principle for planetary exploration spacecraft. In the past, landing gear systems with cantilever designs that incorporate honeycomb materials to dissipate shock energy through plastic deformation have been used, but once tested before launch, the system cannot be used in a real mission. The sky crane system used for the Mars Science Laboratory by NASA can achieve a safe and precise landing, but it is highly complex. This paper introduces a momentum exchange impact damper (MEID) that absorbs the controlled object׳s momentum with extra masses called damper masses. The MEID is reusable, which makes it easy to ensure the landing gear׳s reliability. In this system, only passive elements such as springs are needed. A single-axis (SA) model has already been used to verify the effectiveness of MEIDs through simulations and experiments measuring the rebound height of the spacecraft. However, the SA model cannot address the rotational motion and tipping of the spacecraft. This paper presents a two-landing-gear-system (TLGS) model in which multiple MEIDs are equipped for two-dimensional analysis. Unlike in the authors׳ previous studies, in this study each MEID is launched when the corresponding landing gear lands and the MEIDs do not contain active actuators. This mechanism can be used to realize advanced control specifications, and it is simply compared with previous mechanisms including actuators, in which all of the MEIDs are launched simultaneously. If each MEID works when the corresponding gear lands, the rebound height of each gear can be minimized, and tipping can be prevented, as demonstrated by the results of our simulations.
... Note that the vertical and horizontal velocities of the multirotor lander can be regulated using the altitude and attitude controllers for stable and soft landings. The use of lightweight plastic deformable material as the landing base 55,56 for soft landings along with proximity sensors attached to height-adjustable legs are recommended herein for future planet landers to complete the planet exploration lucratively. ...
Although numerous models of aerial‐robots/drones and planet landers have been demonstrated to fly autonomously in natural and manmade environments for far‐reaching scientific and technological change to help humankind, no drone flowed yet with a push‐pull dual‐head electromagnetic propulsion (EMP) system ensuring unrestricted flight endurance. The precept of EMP is eminent as it hastens an object using a flowing electrical current, either to charge a field or opposing a magnetic field for locomotive use. Here we present a proof of concept to demonstrate the capability of a newly invented variable speed propulsion and energy conversion system for uninterruptedly generating the reciprocating motion of a magnetic piston by a solar battery‐driven polarity changer timing circuit together with a laser‐based timing circuit for redundancy. The reciprocating crusade of the magnetic piston could be successfully converted into rotary motion to generate continuous power for various multidisciplinary applications on Earth and the other planets effectively in lieu of long‐lasting rechargeable batteries. The proposed concept can also be used for devising various systems and subsystems from underwater to outer space by using light weight supermalloy, which ensures high magnetic fluxes with relatively low current. Lucrative applications include nanomaterial‐enabled locomotive applications. Aerial robots regulated with the EMP system could be used for fostering pharmaceutical florae in the international space station for drug design to negate the recently discovered phenomenon of Sanal flow choking in cardiovascular system at gravity and/or microgravity conditions. This concept is originated from mind and aimed for lucrative product developments of yocto to yotta scale energy systems and beyond by discovering new magnetic materials through the fourth industrial revolution. Herein, a proof of the concept of an unrestricted solar‐battery driven push‐pull electromagnetic propulsion and energy conversion device by use of light weight high power magnetic materials is presented.
... Konsep dasar dari MEID seperti yang digambarkan pada gambar 1 dibuat dari teori benturan tiga bola, dimana bola pertama dianggap sebagai gaya eksitasi atau eksternal dari luar yang membentur massa utama yang dipresentasikan oleh bola kedua, sedangkan bola ketiga mempresentasikan massa damper yang berfungsi mereduksi energi kinetic yang dipindahkan dari bola kedua menggunakan metoda perubahan momentum. Gambar 1. Metoda benturan 3 bola berdasarkan teori ayunan newton [12] Metoda MEID seperti yang digambarkan oleh gambar 2 dianggap mampu mereduksi akselerasi maksimum pada vibrasi [13] dan dapat diaplikasikan pada benda seperti mesin tempah dan roda pendaratan pada pesawat terbang [13]. Pada sistem PMEID, perpindahaan energi maksimum dari massa utama kepada massa peredam memiliki durasi yang sama dengan benturan dari massa damper ke massa utama [13]. ...
Vibration that occurs due to excessive impact can damage the construction of an object. Excessive Impact which usually occurs at certain times such as aircraft landing gear collisions with runways that can be fatal if the vibrations produced cannot be controlled properly. One method to reduce vibration caused by excessive impact is called PSMEID (Pre-Straining Momentum Exchange Impact Dumper), which in this case utilizes momentum from a period placed in the main period in which the direction of the style is opposite to the force produced by the collision. In previous studies the PSMEID system was activated shortly after the collision, due to the absence of a sensor mechanism to detect the vibrations and movements of objects that occur. In this case, this research tries to design a sensor system that can detect the movement of objects before an Excessive impact occurs. By knowing the position and condition of the object just before the collision, it can be predicted the time of the collision so that the time of mass release with a spring push that has been stretched (pre-straining) in the opposite direction from the direction of collision gives more optimal results to reduce vibrations from the collision. This study designed various of sensors system consisting of vibration sensors, acceleration sensors and proximity sensors that work in such a way that the PSMEID activation time is close to / equal to the time of the initial collision so that momentum and acceleration can be reduced. In the initial testing this sensor system only involves vibration sensor, where PSMEID can be activated 32 millisecond.
Keywords : Excessive Impact, PSMEID
Abstrak
Getaran yang terjadi diakibatkan oleh benturan yang berlebihan (Excessive Impact) dapat merusak kontruksi sebuah benda. Excessive Impact yang biasanya terjadi pada waktu tertentu saja seperti benturan roda pendaratan pesawat dengan landasan pacu yang dapat berakibat fatal jika getaran yang dihasilkan tidak dapat dikontrol dengan baik. Salah satu metoda untuk mereduksi getaran yang diakibatkan dari (Excessive Impact) disebut sebagai PSMEID (Pre-Straining Momentum Exchange Impact Dumper), dimana dalam hal ini memanfaat momentum dari sebuah masa yang ditempatkan pada masa utama yang arah gayanya berlawanan dengan gaya yang dihasilkan oleh benturan. Pada penelitian sebelumnya system PSMEID diaktifkan sesaat setelah terjadinya benturan, karena tidak adanya mekanisme sensor untuk mendeteksi vibbrasi dan pergerakan benda yang terjadi. Maka dalam hal ini, penelitian ini mencoba merancang sistem sensor yang dapat mendeteksi pergerakan benda sebelum terjadinyanya Excessive impact. Dengan mengetahui posisi dan kondisi benda sesaat sebelum terjadi benturan maka dapat diprediksi waktu benturan sehingga waktu pelepasan massa dengan dorongan pegas yang sudah diregangkan (pre-straining) dengan arah yang berlawanan dari arah benturan memberikan hasil yang lebih optimal untuk mereduksi getaran dari benturan yang terjadi. Penelitian ini merancang system multinsensor yang terdiri dari sensor vibrasi, sensor percepatan dan sensor jarak yang bekerja sedekian rupa sehingga waktu aktifasi PSMEID mendekati/sama dengan waktu terjadinya benturan awal sehingga momentum dan percepatan dapat direduksi. Pada pengujian awal system sensor ini hanya melibatkan sensor vibrasi saja, dimana PSMEID mampu diaktifkan 32 ms.
Kata Kunci : Excessive Impact, PSMEID
... In this work, we will focus on the last phase that which deals with what happens immediately prior to and after touchdown. (VTOL) vehicles [34], suspension system for rovers [24], and several others [25,35]. Reusability is especially important for the concept of hoppers [36][37][38], vehicles able to repeatedly land and takeoff from the surface of a planet. ...
Landing safely is the key to successful exploration of the solar system; the mitigation of the connected effects of collision in mechanical systems relies on the conversion of kinetic energy into heat or potential energy. An effective landing-system design should minimize the acceleration acting on the payload. In this paper, we focus on the application of a special class of nonlinear preloaded mechanisms, which take advantage of a variable radius drum (VRD) to produce a constant reactive force during deceleration. Static and dynamic models of the mechanism are presented. Numerical results show that the system allows for very efficient kinetic energy accumulation during impact, approaching the theoretical limit.
... The establishment of coordinate system In the landing point longitude circle plane, set the intersection between the line of month heart/trajectory perilune and the moon surface as the coordinate origin, the spacecraft perilune velocity direction is as x axis, the moon heart directed to perilune direction as y axis. Equivalent treatment of variable parameters Because the reverse thrust in the main reducer stage is from the fuel consumption, the craft weight gradually reduces [5]. If the weight is seen as a function of time, ...
Based on the operation data and basic parameters of spacecraft, soft landing process is done reasonable simplification equivalent. Without losing the accuracy, this paper proposes the control scheme at obstacle avoidance stage. The landing preparation track is accord with the energy conservation and the Kepler's motion law. The control strategy of soft landing can use differential to solve the optimal control strategy using Newton classical mechanics law. It has a certain practical application value in the spacecraft landing parameters calculation and track design. Keywords-Linear discrete, Iteration method, Genetic algorithm, Gray matrix. Matlab
The probes landing on the surfaces of the asteroids can increase the scientific return of the exploration missions and also promote the development of deep space resources. Because of its excellent applicability to the uneven terrain and a lighter configuration than the four-legged mechanisms, the three-legged cushioning mechanisms are suitable for dissipating the impact energy and then quickly stabilizing the probe attitude when the probe lands on the micro-gravitational surfaces of the asteroids. Research on the landing dynamics of the probe facilitates to the design of the landing-cushioning mechanism and the optimization of its configuration, as well as the assessment of the landing safety. Comparing with the previous extensive related literature focusing on landing dynamics of the probes assisted by the four-legged cushioning mechanisms, this paper studies creatively the planar dynamics considering the asymmetric characteristic and the leg-leg coupling to understand the landing process of the asteroid probe with the three-legged cushioning mechanism and thereby to optimize the configuration of cushioning mechanism and assess safety margin of the landing. According to the touchdown status, the asymmetric landing modes are classified and the coupling issue in the construction of the landing models is explained. Consequently, two types of dynamics models describing the two-stages touchdown cushioning process of the probe are established. Then, five significant configuration factors of the cushioning mechanism are extracted, and their values combinations are designed according to the Taguchi orthogonal method. On this basis, the maximum safe landing attitude angles of the probe are solved by using these values combinations as the input conditions under the dangerous situations in different landing modes. The range analysis and nonlinear fitting methods are employed to discuss the influence of the configuration factors on the landing safety margin, and the favorable parameter values of the configuration factors are determined. Next, the influence of the ground obstacle on the landing safety margin and several methods to improve the margin are researched. Finally, the complete attitude changes of the probe in two representative landing cases are analyzed. The results studied in this paper can contribute to configuration optimization of the three-legged cushioning mechanisms and safety assessment of the legged probes landing on the asteroids, as well as to provide a reference for discussing the leg-leg coupling issue received less attention in landing dynamics of the probes with the four-legged cushioning mechanisms.
Focused on an asteroid probe with three-legged cushioning, this paper discusses the effects of the asymmetric configuration and the element forces form of the planarized cushioning mechanism on the method for developing the landing experiment. The main objectives are to present an accurate experimental analysis of the planar landing and to facilitate the construction of a micro-gravity experimental platform through the theoretical analysis in advance. Probe models based on the planar symmetric and asymmetric configurations of the cushioning mechanism were constructed and their parametric characterization was determined. Mathematical models of the element forces on cushioning legs were established and differences between each set of corresponding element forces were analyzed. Then, dynamics models explaining the landing process were established. On this basis, the maximum initial safe attitude angle and the change process of the attitude variables were researched. The results revealed that the asymmetric configuration greatly reduced the safety margin of the attitude angle and it was determined by the M-R(I) landing as 23°. In addition, the simplified version of the ground friction force could be employed for developing the experiment at the initial attitude angle of 20°, but it affected the results at the initial attitude angles of 0°, 5°, and 10°. At the initial attitude angle of 20°, which is more significant as the critical condition for dangerous landing, the normal footpad-ground contact of the merged leg could adopt the same stiffness coefficient as that of the real leg to facilitate the experimental design without affecting the experimental results.
This paper illustrates the dynamic modeling, experimental validation of Reusable Launch Vehicle under symmetric landing mode. Firstly, a new quasi-3D dynamic landing model of vehicle under 2-2 and 1-2-1 symmetric landing mode is established, which can predict the plane motion of the main body and the spatial motion of landing struts and footpads. The strut force, footpad-ground contact force and the liquid spring damper are also included in the model. Secondly, the landing impact experiments are performed for 2-2 and 1-2-1 symmetric landing mode. The main and auxiliary strut force are obtained, along with the force-stroke diagram of damper. By comparing with experimental data, the accuracy of simulation model is verified. It is found that the simulation model possesses good match with tested responses in damping stroke and main strut force. The simulation and experiment also indicate the same trend in auxiliary strut force and main body acceleration. The main discrepancies attribute to the simplified structural flexibility and nonlinear contact.
The landing gear is a critical component of an aircraft as it makes sure that the aircraft returns to the ground safely after flight without any damage. Landing gear is designed to absorb the kinetic energy that is generated upon landing and to dissipate this energy safely throughout the airframe. Designing a landing gear is a difficult task which is further complicated if landing gear needs to be retracted. Major problems are faced because of the kinematics of the landing gear and also due to space constraints in case of retractable landing gears. During landing, the landing gears are subjected to several loads from several direction and often overloading occurs. Aircraft is one of the most complex machines made by man and failure of any one of its components can be deadly. But as other components of the aircraft the landing gears are also subjected to several types of vibrations and fatigue failure. Often structural failure in aircraft, occur due to fatigue cracking and the fatigue failures originate where the material is dynamically stressed the most. This paper gives a review on the research and development going on in the field of landing gears used for commercial, military and space applications. A stable and efficient landing gear can be manufactured, if its material failure is analyzed precisely.
In this paper, the authors propose a novel landing method named “Two-step Landing Method” for small lunar lander which is needed to be designed considering constrains from envelope area of rocket and the weight of the lander. The proposed method enforces intentional body tumbling at the contact of main leg. We analyzed its dynamics by three-dimensional simulations which consider lander’s attitude and lateral velocity and landing site’s slope angle. Numerical simulation models have been designed on Mechanical Dynamics Software “ADAMS”, and lander models refer to “SLIM” which is a small lander proposed by ISAS/JAXA. It is found that the proposed landing method can land on steep slope by tilting body attitude toward inclination direction of landing site. Especially in the case of landing with lateral residual velocity, the proposed method has higher landing stability than conventional landing method.
Momentum exchange impact dampers (MEIDs) were proposed to control the shock responses of mechanical structures. They were applied to reduce floor shock vibrations and control lunar/planetary exploration spacecraft landings. MEIDs are required to control an object’s velocity and displacement, especially for applications involving spacecraft landing. Previous studies verified numerous MEID performances through various types of simulations and experiments. However, previous studies discussing the optimal design methodology for MEIDs are limited. This study explicitly derived the optimal design parameters of MEIDs, which control the controlled object’s displacement and velocity to zero in one-dimensional motion. In addition, the study derived sub-optimal design parameters to control the controlled object’s velocity within a reasonable approximation to derive a practical design methodology for MEIDs. The derived sub-optimal design methodology could also be applied to MEIDs in two-dimensional motion. Furthermore, simulations conducted in the study verified the performances of MEIDs with optimal/sub-optimal design parameters.
Spacecraft landing missions require a soft landing mechanism to prevent a large shock load and tipping over when landing on various types of terrain. The authors previously invented a novel landing mechanism called a telescopic-gear base-extension separation mechanism that operates by means of energy transfer and an adjustable structure. This mechanism passively adjusts the shape of the landing gear according to the landing terrain and transfers the energy of the lander to a spring as potential energy. The outstanding performance of this landing mechanism was demonstrated analytically in a previous study. However, its feasibility was not confirmed, and an effective parameter design method for various shapes of terrains was not presented. Therefore, in this study, two-dimensional experimental investigations are conducted using a small-scale prototype to assess the feasibility of the landing mechanism for several types of terrain. An effective parameter design approach based on a mathematical model derived from the experimental results is presented in this paper. To improve the robustness of the landing mechanism, the lengths of the telescopic gears should be as large as possible, and the spring stiffness should be tuned within a certain range. For sloped ground in particular, the width of the lander is an additional important design parameter; a smaller width is preferable in theory. A robustness study and several important notes on the practical design aspects of the landing mechanism are summarized in this paper.
This paper discusses landing response control methods of planetary exploration spacecrafts on the basis of momentum exchange principles. Concretely, the methods adopt momentum exchange impact dampers (MEIDs) that absorb the controlled object's momentum with extra masses close to the object (damper masses). For example, this paper shows Upper-MEID (U-MEID) that launches the damper mass upward and Lower-MEID (L-MEID) that drops the damper mass downward. Moreover, Generalized-MEID (G-MEID) consisting of U-MEID and L-MEID is introduced. The optimal design parameters of the G-MEID mechanism in a single-axis case for the landing of a spacecraft are investigated. Simulation investigation verifies that the G-MEID mechanism is superior than any other MEID mechanisms from the point of view of reduction of the maximum rebound of the spacecraft. Moreover, the effectiveness of the G-MEID whose U-MEID adopts an active actuator (G-Hybrid MEID) is verified in the view of the rebound reduction performance and the robustness against the landing ground stiffness and spacecraft's mass variations.
抄録
This paper describes modeling and simulation for a lunar lander “SELENE-B.” The simulation model has been designed on Mechanical Dynamics Software “ADAMS.” Body frame consists of rigid bodies, which has four elastic legs. Specific definitions have been applied in order to describe characteristic of honeycomb core, and also in order to express contact dynamics with lunar surface. Parameters setting for contact and friction forces are based on ground tests for landing on the simulant imitating lunar regolith. Representative landing patterns have been simulated, and motion analysis has been examined. Also, stable and unstable landings have been evaluated.
When a spacecraft lands, a large shock load can lead to undesirable responses such as rebound and tripping. The authors previously discussed the problem of controlling these shock responses using momentum exchange impact dampers. An active/passive hybrid momentum exchange impact damper, which included an active actuator, was proposed. The momentum exchange impact dampers' performances are evaluated by the maximum rebound height, which is proportional to the mechanical energy of the spacecraft. However, the time responses of the energies have not been explained. In addition, the effectiveness of momentum exchange impact dampers was evaluated only in a one-dimensional motion simulation. This paper includes theoretical analyses, simulation studies, and experiments. The time responses of the energies of momentum exchange impact dampers are discussed. This paper proposes a robust landing gear system for spacecraft using a hybrid momentum exchange impact damper and evaluates its robustness against ground stiffness variation. First, momentum exchange impact dampers are applied to a mass-damper-spring model, which takes the ground viscosity into account. Next, the proposed model's effectiveness is verified by simulation studies and some experimental results. Finally, this paper studies two-dimensional motion analyses to address rotational motion.
When a spacecraft lands, the large shock load can lead to undesirable responses, such as rebound and trip. The authors have previously discussed the problem of controlling these shock responses using momentum exchange impact dampers (MEIDs). However, the optimal design parameters of MEIDs for spacecraft landing have not yet been addressed. These parameters are crucial for MEID applications. This paper discusses the parameters of Passive-MEID (PMEID) for a single-axis falling-type problem, which is the most fundamental problem. It is found that the rebound height is proportional to the mechanical energy of the spacecraft. Thus, the optimal design parameters of the PMEID correspond to the parameters that minimize the mechanical energy. A PMEID with the optimal design parameters is called optimal PMEID in this paper. In order to improve the performance of the optimal PMEID, this paper proposes a novel MEID — HMEID (active/passive-hybrid-MEID). The HMEID combines actuators with passive elements such as contact springs. Based on the optimal design results for the MEIDs, this paper applies a stiffness control to the HMEID in order to suppress the mechanical energy further. Simulation studies reveal that the HMEID can effectively reduce the influence of shock responses. The robustness of the HMEID against the landing ground is shown. The feasibility of the HMEID is also discussed. The HMEID is superior to a PMEID, even if the actuator has a dynamics with a large electric time constant.
Upon landing of a spacecraft, a large shock load can lead to such undesirable responses as rebound, swing vibration, sideslip, and tripover of the spacecraft. This paper discusses the problem of controlling these shock responses by means of momentum exchange impact dampers, especially the active momentum exchange impact damper. The momentum exchange impact dampers are classified into two types: the passive momentum exchange impact damper composed of passive elements and the active momentum exchange impact damper that includes active actuators. The active momentum exchange impact damper can greatly reduce the effects of shock responses. First, landing systems consisting of momentum exchange impact dampers are designed to conduct simulations and model a two-legged system. The passive momentum exchange impact damper mechanism is a one-degree-of-freedom vibration system. The active momentum exchange impact damper mechanism employs electrical motors as actuators in addition to the passive momentum exchange impact damper components. To assess the effectiveness of the control system, three cases are simulated: without momentum exchange impact damper, with passive momentum exchange impact damper, and with active momentum exchange impact damper. The results of the simulations show that the active momentum exchange impact damper is most effective in controlling spacecraft landing responses.
Reduction of landing impact of spacecraft by means of momentum exchange
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On estimation methods of impact force at landing on lunar and planetary sandy surface (Ph.D. Dissertation), Graduate University for Advanced Studies
- T Yokoyama
T. Yokoyama, On estimation methods of impact force at landing on lunar and planetary sandy surface (Ph.D. Dissertation), Graduate University for Advanced Studies, Japan, 2008, 100–111 (in Japanese).