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An active suspension system for lunar crew mobility
Abstract
This paper describes the design and control of the first generation active suspension for NASA's Chariot rover and Lunar Electric Rover (LER). Within the paper is a general overview of the needs and benefits of active suspensions for crew mobility systems on the lunar surface. In the spectrum of active suspensions, the Chariot system falls into the category of a series active or low bandwidth suspension. The passive suspension elements absorb the high frequency content of driving over rugged terrain and the active element sets the height of the suspension allowing the vehicle to conform to the terrain. This suspension system is capable of raising and lowering the vehicle, adjusting roll and pitch attitude for docking operations, leveling the chassis against gravity, and balancing the force across the six wheels during low speed operations. In addition to the existing system, initial results of an incremental design upgrade are discussed and future considerations for suspension systems for the lunar surface are described.
... Among them, it is worth highlighting the use of actively articulated or adaptive suspensions. These systems have been applied to 4-wheel rovers (Iagnemma et al., 2003b;Bartlett et al., 2008), crew-piloted vehicles (Bluethmann et al., 2010), and hybrid wheeledlegged robots (Schäfer et al., 2011;Cordes et al., 2014). In all of these cases the locomotive capabilities are improved by the possibility to control the robot's attitude, adapting the position of the center of gravity to maximize performance based on the surrounding terrain conditions (Fig. 3), at the expense of some added complexity. Figure 3: Adaptive suspensions capable of actively changing the robot wheel base allow for a flexible control of its attitude, improving its overall performance when driving on uneven surfaces. ...
... Apollo 15 astronauts even reported that they had experienced a full takeoff in which the 4 wheels of the LRV had instantly lost contact with the ground (Costes et al., 1972). The problematic combination of fast traveling velocities with a reduced gravity field was also present while steering and overcoming slopes of loosely-compacted soil (Bluethmann et al., 2010). Turning at about 1.4 m/s made the wheels skid in the lateral direction leading to a reduced side-to-side traction responsiveness and an immediate loss of braking effectiveness (NASA, 1971;NASA, 1972). ...
... Apollo astronauts also informed that climbing and cross driving steep slopes was like being on top of a roller coaster where the sensation of falling off the vehicle was constantly present. The bouncing of the vehicle suspension together with the open frame design of the LRV did not help in mitigating this effect (Bluethmann et al., 2010). In addition, when attempting to cross drive slopes the downhill wheels tended to dig into the soft soil forcing the astronauts to reduce the speed (Costes et al., 1972). ...
Despite the success so far accomplished in the robotic exploration of the Moon and Mars, the constraints associated with newly proposed mission concepts manifest the need for a faster surface prospection. Increasing driving velocities is being considered as a potential solution to the requirements introduced by these missions. This review presents the benefits and foreseeable challenges of using faster locomotive solutions for space exploration. Information is provided regarding the set of missions that would benefit most from faster locomotive capabilities. Starting by understanding the theoretical framework governing the interaction of wheeled robots operating over loose, sandy terrains, we delve into the foundation of Bekker's classic terramechanic equations—the most frequently used method to predict mobile robots off‐road performance. We highlight its limitations and review the efforts that have been made to expand the range of application of these theories to dynamic wheel–soil interactions. We analyze the existing experimental evidence on the effects of increasing traveling velocities under earthbound, off‐road conditions. By paying special attention to previous experiences on the lunar surface, we outline the challenges that the combination of irregular terrains and a reduced‐gravity field may pose to a fast‐moving exploration rover. The principles, mathematical models, experimental evidence, and experiences presented in this review are meant to aid in the identification of poorly understood and insufficiently studied aspects regarding high‐speed extraterrestrial surface mobility.
(Access the article here: https://onlinelibrary.wiley.com/doi/full/10.1002/rob.21912)
... Type-II PSMSs are small unpressurized vehicles similar to the lunar roving vehicle (LRV) [10]. Type-III PSMSs, as exemplified by the LER [11] and ATHLETE [12], are multi-wheeled pressurized lunar rovers (MWPLRs), which are currently in the development stage and would enable astronauts to drive in pressurized capsules and explore far from the lander where no unpressurized rovers can reach. Because of their ability to metamorphose into mobile habitats [13], Type-III PSMSs have been listed by many countries in their future lunar development plans. ...
... In summary, Configurations 6 and 7 satisfy the DOF and motion requirements but do not maintain geometric characteristics during the vertical motion of the MP, resulting in the transformation to the sixth layout. They also exist as instantaneous configurations in Configurations 10 and 11. [8][9][10][11]. In Layout 6 for the MP constrained space, the lines are concurrent with two lines, and the design flow of Configurations 8-11 under Layout 6 is as follows. Configuration 8: First, the constraint space u(N 1 , n 1 ) ∪ u(N 2 , n 2 ) of the MP is constructed as shown in Fig. 6(a). ...
... Así, los robots híbridos hacen uso de dos o más mecanismos de locomoción a la vez, por ejemplo: uso de patas con ruedas (Bruzzone et al., 2017); otros robots cambian su forma para amoldarse al terreno y poder avanzar (Li et al., 2009). En otros casos, algunos manipuladores móviles han sido diseñados para usar su brazo en distintas estrategias, las cuales incluyen: movimientos compensatorios y contacto del brazo con el suelo (García et al., 2015a); y finalmente, una de las soluciones más ampliamente aceptadas en la mayoría de robots consiste en el uso de un sistema de suspensión que ayuda al robot a mantener la estabilidad al vuelco, mejora el agarre del robot al equilibrar las fuerzas de reacción con el suelo, lo cual implica una mejora en el direccionamiento (Bluethmann et al., 2010), y por último, mejora el confort en el robot al disminuir las vibraciones y aceleraciones que se producen al desplazarse sobre terrenos irregulares (Chen et al., 2017). ...
En este artículo se estudia el efecto que produce el sistema de suspensión sobre la estabilidad al vuelco y la capacidad de direccionamiento en un robot móvil Skid Steer, cuando este se enfrenta a distintas discontinuidades del terreno: descenso (frontal y lateral) y ascenso sobre escalones, además del desplazamiento sobre zanjas. Específicamente, se estudió el instante cuando se generan cargas de impacto producto del movimiento del robot sobre la irregularidad del terreno. En cada caso se hizo un análisis correlacional del efecto sobre la estabilidad al vuelco y el direccionamiento (cuantificadas con métricas fundamentadas en las fuerzas de reacción de las ruedas con el suelo), al variar cuatro parámetros que definen el sistema de suspensión: constante de rigidez en los resortes, constante de amortiguamiento en los amortiguadores y las constantes de rigidez y amortiguamiento en las ruedas. Por último se estimó para cada caso, qué magnitudes deberían adquirir estos parámetros para garantizar una mejor estabilidad y direccionamiento del robot.
... Así, los rovers (vehículos de exploración espacial) comúnmente poseen un sistema de tracción conformado por eslabones y ruedas. Los eslabones, por lo general, están acoplados a actuadores que permiten cambiar la orientación de los mismos, logrando una mejor conformidad del robot con la superficie del terreno, lo cual se pudiera traducir en una mayor eficiencia en el desplazamiento sobre el terreno irregular y una mejora en la estabilidad del robot (Bluethmann, et al., 2010). ...
Este artículo tiene por objetivo describir a Lázaro, el cual es un pequeño robot móvil que posee un brazo diseñado especialmente para propiciar un punto adicional de contacto con el suelo que puede utilizarse para mejorar la estabilidad al vuelco y superar obstáculos. Específicamente, se aborda la descripción de la estructura mecánica así como los componentes electrónicos destinados a percepción, comunicación y control. Posteriormente, se revisan las características de funcionamiento de este robot, en cuanto a su cinemática, arquitectura de control, modos de operación e interface. Finalmente, se hace una descripción de algunas pruebas de funcionamiento.
... Most of the research conducted on active suspension systems (e.g. [3]- [6]) considers the actuator as an ideal force source and neglects its internal dynamics that interacts in many ways with the rest of the vehicle dynamics. In fact, most of the actuators exhibit nonlinear behaviour [7], have a limited bandwidth [8], and are exposed to external disturbances which makes the controller design more complicated and sets additional requirements on the controller design process. ...
Active suspension systems ease the conflict between comfort and handling. This requires the use of suitable actuators that in turn need to be efficiently controlled. This paper proposes a model-based control approach for a nonlinear suspension actuator. Firstly the concept is derived in the linear framework in order to simplify the synthesis and analysis phase. There a linear model of the actuator is proposed and discussed. Further, this design phase includes a comparison between model-free PID controllers and a newly proposed two-degree-of-freedom controller which allows one to shap reference and disturbance responses separately. Subsequently, the two-degree- of-freedom controller, which proves to be superior, is adapted to the nonlinear framework by considering a linear parameter varying representation of the nonlinear plant. Finally, the nonlinear controller is implemented in a test car confirming the concept applicability to real hardware.
... Some recent projects are illustrated in Figs. 2 and 3. The following technologies have been developed, typically to a Technology Readiness Level of 3 to 6: methods to prepare work sites and landing pads by grading and stabilizing the soil [23,40]; tools and methods for resource prospecting [41][42][43][44]; mobility systems for planetary surfaces [46,47]; lunar/martian excavators [48] including methods to reduce the excavation forces to work in low gravity with low-mass vehicles [49,50]; ice mining technology for cryogenically cold volatiles [51]; methods to transport soil in and out of chemical processing modules in low gravity [52]; beneficiation technologies to concentrate desirable minerals [53] and particle sizes [54] in the lunar soil; chemical plants to extract oxygen from lunar or martian soil [55][56][57][58]. We need further work in all these areas as well as: construction techniques; chemical processing to make a variety of materials from the volatiles (including rubber, plastic, and hydrocarbons like methane); mining and refining metals from regolith and from M-type asteroids; methods to work in the ultra-low gravity of asteroids; additive manufacturing that prints with space-derived materials; advanced additive manufacturing that utilizes multiple material streams to print complex machinery; and applications specifically designed for Mars. ...
Building a starship within the next 100 years is an audacious goal. To be successful, we need sustained funding that may be difficult to maintain in the face of economic challenges that are poised to arise during these next 100 years. Our species' civilization has only recently reached the classification as (approximately) Type-I on the Kardashev scale; that is, we have spread out from one small locality to become a global species mastering the energy and resources of an entire planet. In the process we discovered the profound truth that the two-dimensional surface of our world is not flat, but has positive curvature and is closed so that its area and resources are finite. It should come as no surprise to a Type-I civilization when its planet's resources dwindle; how could they not? Yet we have gone year by year, government by government, making little investment for the time when civilization becomes violent in the unwelcome contractions that must follow, when we are forced too late into the inevitable choice: to remain and diminish on an unhappy world; or to expand into the only dimension remaining— perpendicularly outward from the surface into space. Then some day we may become a Type-II civilization, mastering the resources of an entire solar system. Our species cannot continue as we have on this planet for another 100 years. Doubtless it falls on us today, the very time we intended to start building a starship, to make the late choice. We wished this century to be filled with enlightenment and adventure; it could be an age of desperation and war. What a time to begin an audacious project in space! How will we maintain consistent funding for the next 100 years? Fortunately, saving a civilization, mastering a solar system, and doing other great things like building starships amount to mostly the same set of tasks. Recognizing what we must be about during the next 100 years will make it possible to do them all.
... La suspensión activa incorpora las restricciones de confort y maniobrabilidad (Rivin, 1985) (Akcay and Türkay, 2008). Además, considera las irregularidades del terreno en el diseño del modelo (Fruehauf et al., 1985) (Alexandru and Alexandru, 2011) y permite controlar las fuerzas trasmitidas (Malek and Hedrick, 1985) (Bluethmann et al., 2010 ). El desarrollo en microelectrónica de las ultimas décadas ha facilitado su aplicación y generalmente es incluida en los vehículos de alta gama (Hrovat, 1990) (Thompson and Davis, 1991) (Koch et al., 2010). ...
Resumen El propósito de este artículo es efectuar una revisión del estado del conocimiento en el modelado y control de los sistemas de suspensión activa y semiactiva. Se analizan las principales características de los diferentes tipos de sistemas de suspensión: pasiva, activa y semiactiva. Respecto al modelado y simulación de los sistemas de suspensión, se examinan los distintos enfoques, herramientas y aplicaciones en el contexto de la dinámica vehicular. Además, para el modelo de un cuarto de vehículo, ampliamente utilizado en la literatura, se ofrece su desarrollo mediante ecuaciones diferenciales, función de transferencia, y ecuaciones de estado, incluyendo soluciones y simulaciones en Simulink y SimMechanics. En cuanto al control, se revisan las principales estrategias para la suspensión de vehículos y se apuntan aplicaciones en otros campos de la ingeniería. Copyright c 2011 CEA.Publicado por Elsevier España, S.L. Todos los derechos reservados.
A Lunar Crewed Vehicle(LCV) with improved manoeuvrability, mobility and ride comfort is required for astronauts to conduct long-range scientific investigations and resource utilisation on the Moon's surface. This paper concentrates on designing a novel multifunctional compliant suspension for LCV to improve the above mentioned performance. Firstly, based on the requirement of high-speed traversing on the rough Lunar terrain, the required type of suspension motion is identified and the demanded suspension mechanism is obtained through structural evolution. Then, the kinematic analysis of the proposed suspension mechanism is conducted, and the steering kinematic model of the whole vehicle is established. A compliance analysis is completed, taking into account the actual design characteristics of the suspension mechanism. A multi-degree-of-freedom dynamics model of the vehicle is developed, considering both wheel-ground separation and the deformation of wheels and soil. Simulations are conducted to verify full vehicle performance with the proposed suspension, and the results reveal that the design features better mobility and comfort in rough terrain with minimum turning radius, peak longitudinal acceleration and root-mean-square reduced by 9.5%, 45.1%, and 21.4%, respectively
Suspension design is one of the important parts in the research field on lunar rover mobile system. To conduct detailed dynamic analysis on the new type of suspension, this paper presents a new type of six link double ring lunar rover suspension model based on ADAMS virtual simulation software. And, this paper designs the lunar rover path tracking neural network controller. Simulation and test results show that the new lunar rover suspension has strong ground adaptability, obstacle surmounting capability and anti-overturning ability compared to classic suspension, and the neural network controller based on the new suspension has good tracking ability. The research results provide a reference for autonomous navigation control on lunar rover.
This paper elaborates a Heavy-Payload Omnidirectional Robot (Hobot) that can efficiently carry heavy payloads on uneven indoor floors. It consists of four Steer-able Differential-Geared Dual-Wheels (SDD), composed a differential-geared dual-wheel, a passive tilt-adapting joint and a suspension washer. In order to combine heavy-payload and omnidirectionality, the mechanism is designed by means of evaluating its four qualitative criteria and two quantitative metrics. The criteria are ground contact, energy efficiency, type of omnidirectionality and internal stress distribution. The metrics are Support Force Isotropy (SFI) and Critically Loaded Mass (CLM). The feasibility of Hobot prototype was verified by omnidirectional motion experiments under heavy payloads. The results show that Hobot can efficiently carry a total mass of 2,130kg under speed of 0.3m/s using only an average power of 646W.
A balanced electro-mechanical system must have the openness now represented by the electricals (computer chips, power boards, standardized interfaces, domain-relevant operational software) and the reconfigurability to not only meet the needs of ever-changing tasks, but also enable rapid assembly, repair, and refreshment on demand by means of highly-certified components made available by means of a competitive supply chain. This, then, requires a command/response in milli-sec for multi-input/multi-output (MIMO) systems that are normally perceived as highly non-linear and highly coupled (i.e., unsolvable by standard analytic tools).
Criteria-based decisions in milli-sec essentially linearize these systems to make strictly algebraic processes viable with little or no uncertainty so long as the operational criteria have clear physical meanings. The human command (trains, surgery, aircraft, automobiles, etc.) in concert with semi-autonomous processes can be put into balance where each plays its relevant role. The missing ingredient in this accelerated development of the tech base for the mechanicals is the intelligent actuator (i.e., the action part of the full physical system) as the computer chip is to the electrical system.
Las sistemas de suspensión activa y semiactiva se utilizan con mucha frecuencia en la industria automotriz, aeroespacial, civil, etc. ya que permiten un mejor control de la vibración a la que está expuesta toda estructura mecánica en movimiento o bajo la acción de fuerzas externas. Para el diseño del controlador de estos sistemas se requiere de la elaboración de un modelo que reproduzca de manera rápida y efectiva
la cinemática y la dinámica de la suspensión. Así, esta tesis propone aportaciones para el modelado analítico y control inteligente de estos sistemas.
En primer lugar, se propone un modelo analítico bidimensional de una suspensión McPherson. El desarrollo de este modelo matemático está basado en las ecuaciones del movimiento mediante la utilización de la técnica de la matriz de desplazamiento y en combinación con las ecuaciones de Euler-Lagrange aplicadas a la dinámica del sistema en términos de sus coordenadas generalizadas. Asimismo, se presenta un modelo analítico de determinación de los parámetros equivalentes para el sistema de suspensión McPherson, usando los conceptos de centro instantáneo de rotación y razón de instalación. Se obtiene una expresión general para la rigidez equivalente del resorte en función del movimiento vertical del neumático, la cual incluye el comportamiento no lineal. Después, se propone la aplicación del método de optimización por enjambre de partículas para el ajuste de los factores de escala de un controlador borroso normalizado. Este controlador borroso basado en reglas heurísticas modifica la fuerza del actuador del sistema de suspensión activa en base a la realimentación del error y la tasa de error del desplazamiento de la masa suspendida. Se ha definido una función objetivo no lineal para minimizar la suma de los errores cuadráticos del desplazamiento del chasis en un determinado periodo de tiempo y la sobreoscilación. Este método se ha comparado experimentalmente con otras estrategias de control sobre una planta física.
A taxonomy of planetary exploration rovers is presented, followed by a review of systems used in missions and in an experimental phase. The baseline design emerges as four or six wheels, rocker-bogie based passive suspension and all wheel driving/selected wheel steering. A trend is also apparent in the use of wheel - legged hybrid locomotion. The performance metrics are presented by which the differing configurations of the locomotion subsystem for wheeled rovers with a passive suspension may be systematically evaluated. The taxonomy and aggregated metrics presented in this paper aid in the comparison and selection of rover characteristics, while the baseline design is a representative example of current practices and future trends.
The All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE) is a modular mobility and manipulation platform being developed to support NASA operations in a variety of missions, including exploration of planetary surfaces. The agile system consists of a symmetrical arrangement of six limbs, each with seven articulated degrees of freedom and a powered wheel. This design enables transport of bulky payloads over a wide range of terrain and is envisioned as a tool to mobilize habitats, power-generation equipment, and other supplies for long-range exploration and outpost construction. As a milestone for the 2010 fiscal year, ATHLETE demonstrated the long-range traversing capability of the wheel-on-limb concept. ATHLETE was subjected to eight weeks of traverse testing and demonstrations over rolling natural terrain at two distinct field locations: Hahamongna Watershed Park in Pasadena, CA and the Black Point Lava Flow region north of Flagstaff, AZ. During this period, ATHLETE traversed more than 80 km in total distance, increasing the cumulative traverse distance of all ATHLETE prototypes almost tenfold. This paper evaluates the mobility performance of ATHLETE during these long-range traverses and discusses recent upgrades to the onboard driving algorithms to improve traverse speed and effciency. © 2011 by the American Institute of Aeronautics and Astronautics, Inc.
In the literature, mobile robots featuring both omni-directional and rough-terrain mobility are typically realized by heavy and complicated mechanisms. In considering real outdoor applications, such as hazardous site-inspections or scientific investigations, however, it is desired to develop small and light-weight robots by focusing on the mechanical simplicity and toughness. The primary objective of this study is to investigate and to realize an omni-directional mobile robot on unpaved rough terrain by small, light-weight, simple mechanism. For this purpose, we propose a new concept of wheel structure as well as an omni-directional moving robot. The new wheel, named globular metal spring wheel and composed simply of several super-elasticity-material rods, has not only omni-directional functionality but also properties of light weight, mechanical simplicity and external shock absorbing function. With this globular wheel, a new omni-directional mobile robot, “Eggbeater”, is also developed to evaluate the mobility performance. This paper presents our proposal and development of the globular metal spring wheel and the omni-directional rough-terrain mobile robot, and discusses performance evaluation experiments.
To effectively explore the lunar surface, astronauts will need a transportation vehicle which can traverse all types of terrain. Currently, the National Aeronautics and Space Administration's (NASA) is investigating two lunar rover configurations to meet such a requirement. Under the Lunar Electric Rover (LER) project, a comparison study between the unpressurized rover (UPR) and the small pressurized rover (SPR) was conducted at the Black Point Lava Flow in Arizona. The objective of the study was to obtain human-in-the-loop performance data on the vehicles with respect to human-machine interfaces, vehicle impacts on crew productivity, and scientific observations. Four male participants took part in four, one-day field tests using the exact same terrain and scientific sites for an accurate comparison between vehicle configurations. Subjective data was collected using several human factors performance measures. Results indicate either vehicle configuration was generally acceptable for a lunar mission; however, the SPR configuration was preferred over the UPR configuration priminarly for the SPR's ability to cause less fatigue and enabling greater crew productivity.
Bose Corp. has developed an automobile active suspension system that uses speaker technology to provide a more smooth ride. The Bose system equips each wheel with its own linear electromagnetic motor, similar to those that propel modern roller coasters. The motor works not by revolving but by telescoping up or down to do what shocks and springs do, but much faster. Algorithms manage the car as a whole, preventing body roll during turns and keeping the car from dipping forward when it stops. The company drew on its experience with sound reproduction. The voice-coil technology that drives Bose speakers proved perfect for driving the linear motors, because both applications modulate high-frequency electrical pulses in response to randomly occurring events. Indeed, the suspension's motors may be regarded as the world's strongest quadraphonic speakers, even though they hardly make a sound.
As NASA refines its plans for the return of humans to the lunar surface, it becomes very clear that surface mobility will be critical to outpost buildup and exploration activities. NASA's Exploration Technology Development Program is investing in a broad range of surface mobility projects. Within this range of projects falls a rover vehicle, capable of moving suited crew members and cargo. A prototype, known as Chariot has been developed. This prototype vehicle is a multipurpose, reconfigurable, modular lunar surface vehicle. And, with the right attachments and/or crew accommodations, Chariot will be capable of serving a large number of functions.
Automotive suspension design is a compromise brought about by the
conflicting demands of ride and handling. We have seen the introduction
of increasingly sophisticated, electronically controlled components
which redefine the boundaries of the compromise. The major elements of a
motor car suspension are summarised by the author. The technology
employed in automotive suspension design covers a wide range of
sophistication, performance and cost and can be categorised as: adaptive
suspension, semi-active suspension, low-bandwidth active suspension, and
four wheel steering systems. The author considers each of these
categories
Apollo 16 Mission Report MSC-07230, available from web site
- Spaceflight Nasa
- Center
NASA Manned Spaceflight Center, " Apollo 16 Mission Report, " MSC-07230, available from web site, http://history.nasa.gov/alsj/a16/A16_MissionReport.pdf, Section 9.8.4.
Apollo 17 Mission Report
- Johnson Nasa
- Space
- Center
NASA Johnson Space Center, " Apollo 17 Mission Report, " JSC-07904, available from web site http://history.nasa.gov/alsj/a17/A17_MissionReport.pdf, Section 10.8.4.
Apollo 17 Mission Report JSC-07904, available from web site http://history.nasa.gov/alsj
- Nasa Johnson
- Space Center