Rover Control Research Articles

Fractional-order Model of the Dynamics of a Flexible Sensing Antenna for Haptic Underwater Applications

This paper develops a mechanism to detect the instant at which an underwater haptic flexible antenna detects an object. This sensor is implemented as an aid to navigation in mobile underwater robots. It is used to localize obstacles by performing an active sensing strategy in which the servomotor system moves the beam back and forth until it hits an object. This impact instant is estimated by our mechanism which subsequently triggers an estimator of the contact point of the antenna with the obstacle and switches the rover control system from free to constrained navigation modes. Our detection mechanism is based on detecting if the difference between a measured force/torque signal and the value predicted by a dynamic model surpasses a threshold. This threshold and, then, the delay in the estimation of the impact instant, depend on the accuracy of this model. Several models have been fitted to experimentally recorded data showing that a fractional-order model of complexity equivalent to that of the standard integer model outperforms by more than five times the accuracy of this last one. This results in a much more efficient impact detection mechanism that has a much lower delay time.

Vibration-Based Recognition of Wheel-Terrain Interaction for Terramechanics Model Selection and Terrain Parameter Identification for Lugged-Wheel Planetary Rovers.

Identifying terrain parameters is important for high-fidelity simulation and high-performance control of planetary rovers. The wheel-terrain interaction classes (WTICs) are usually different for rovers traversing various types of terrain. Every terramechanics model corresponds to its wheel-terrain interaction class (WTIC). Therefore, for terrain parameter identification of the terramechanics model when rovers traverse various terrains, terramechanics model switching corresponding to the WTIC needs to be solved. This paper proposes a speed-independent vibration-based method for WTIC recognition to switch the terramechanics model and then identify its terrain parameters. In order to switch terramechanics models, wheel-terrain interactions are divided into three classes. Three vibration models of wheels under three WTICs have been built and analyzed. Vibration features in the models are extracted and non-dimensionalized to be independent of wheel speed. A vibration-feature-based recognition method of the WTIC is proposed. Then, the terrain parameters of the terramechanics model corresponding to the recognized WTIC are identified. Experiment results obtained using a Planetary Rover Prototype show that the identification method of terrain parameters is effective for rovers traversing various terrains. The relative errors of estimated wheel-terrain interaction force with identified terrain parameters are less than 16%, 12%, and 9% for rovers traversing hard, gravel, and sandy terrain, respectively.

The Archimede Rover: A Comparison Between Simulations and Experiments

In this paper, we propose an in-depth evaluation of the performance of the Archimede rover while traversing rough terrain with loose soil. In order to better analyze this, the reality gap is evaluated when simulating the behavior with an open-source simulator. To this extent, we implement a full model of the rover in the open-source dynamics simulator Gazebo, along with several types of terrains that replicate the experimental conditions. The rover control system is equipped with a kinematics model that allows for driving in different modes. We implement an odometric system aboard the rover, as well as an external optical absolute tracking system as reference. We estimate the drift occurring during driving in different configurations, two types of soil with corresponding wheel geometries. The results show good adherence of the odometry when the rover drives on planar ground; conversely, as expected, a marked influence of slope is seen on wheel drift. The reality gap between simulations and experimental results is kept comparatively small provided that slopes are not present.

Design and Control of Autonomous Rover for Foliage Navigation

Implementation of UGV in civilian applications is getting trendy and normalized due to its solid achievement in executing mission under harsh environments. The UGV foliage environment-oriented applications even attracted the people’s attention in correspond sectors to ease their tasks with guaranteed performance. Given this, the development of the autonomous rover from sensors and control aspects with the consideration of foliage environment interest people to enhance its functionality. To ensure the sensor is not easily affected by the environment factor, the radar and the camera are selected to provide the environment perception to the rover. The approach for a linear Proportional-Derivative (PD) controller with the dynamic modelling of the UGV is also discussed in this paper. The study shows preliminary results that are working.

Linear Prediction of High-Slip Sinkage for Planetary Rovers’ Lugged-Wheels Based on Superposition Principle

Planetary rovers with lugged-wheels are the primary equipment for Mars exploration, and as exploration missions become more complex, rovers are expected move into more challenging terrains. When moving over soft sand or slopes, lugged-wheels experience high slip and heavy sinkage, and an explicit sinkage prediction model for lugged-wheels is not available. This limits the motion control of planetary rovers. Here, we show that wheel sinkage can be divided into static sinkage, rolling sinkage, shearing sinkage, and digging sinkage, based on motion decomposition. Static sinkage is in accordance with the modified Archimedes' theorem, shearing sinkage is proportional to the slip ratio, and digging sinkage is proportional to rim displacement. Furthermore, the superposition principle of sinkage has been proved, and the various types of sinkage were superimposed to obtain an explicit prediction model without terramechanics parameters for lugged-wheels. The single-wheel test proves that the linear model can predict sinkage for slip conditions from 0 to 0.9 with a prediction accuracy of over 90%. The decomposition and modeling of the sub-sinkage further explores the intrinsic of the lugged-wheels’ sinkage, and the linear prediction model provides a theoretical basis for high slip control of rovers.

Towards teleoperation performance and psychophysiological state assessment in the SIRIUS-19 analog campaign

Future lunar bases and long duration space travel have increased the scientific interest in the potentially negative effects that confinement and isolation can have on a crew’s interpersonal behavior, cognitive state and performance. Given the hazardousness of these missions, it seems crucial to analyze the impact of Human Factors on the daily parameters of operators in order to enhance both their safety and performance. In order to progress towards a more global assessment of a confined operator’s cognitive state we propose to analyze subjective and objective measures regarding a professional task. Hence, this study evaluates the correlation between the participants’ performance in a teleoperation task with their reported mood, motivation and their measured cardiac activity during a ground-based analog space mission. The facility considered was the NEK at IBMP in Moscow, Russia. Six participants (3 females; Mean Age=33.4, σ=6.656; 2 Americans and 4 Russians) were confined during 4 months in this facility. Over the period of confinement, they undertook seventeen teleoperation sessions. The teleoperation task consisted in the remote control of a digital rover that was used to collect a sample on the lunar surface. Completion time and accuracy were measured for each session to evaluate the participants’ performance. Training sessions were run before and after the mission. Also, the participants filled shortened versions of the PANAS and the IMI questionnaires to assess their motivation and mood before the task. Additionally, their cardiac activity was measured during the task. The main results are significant Spearman correlations between the reported feeling of confinement and task completion time (ρ=0.375,p<.01) and the reported feeling of confinement with the positive affect component of the mood (ρ=−0.547,p=<0.01). In addition to that, a general decrease of motivation was observed along the mission with the exception of a booster created by the Moon landing phase. The results confirm a link between confinement stressors and the crew’s performance during this professional task as found in other analog missions such as the Lunares and MDRS ones. The project is in continuous expansion, as more data are required to confirm the obtained results and to pursue their analysis. This work was intended to lay the foundations for a neuroergonomic approach of space operators’ assessment.

그라우저 바퀴의 특성을 이용한 탐사 로버의 최적 주행 파라미터 추정

This paper proposes a new method of estimating optimal control parameters such as maximum friction coefficients and the optimal slip ratios for optimal slip control of grouser-wheeled exploration rovers on rough terrain. The exploration rover must classify terrains currently traveling and estimate the parameters required for driving control. Among the existing methods, there are methods of accurately estimating parameters by applying friction coefficients and slip ratios measured using a contact sensor to a friction-slip model. However, there is a problem that the estimation accuracy is very poor in a situation when the slip ratio is small. In this paper, we propose a method of estimating parameters using the motion characteristics of the grouser wheel when slip ratio is small. Though this method, it was confirmed that the parameters were accurately estimated even when the slip ratio was small, and verified through experiments using NASA’s ‘Opportunity’ size exploration rover.

Simultaneous control of trajectory tracking and coordinated allocation of rocker-bogie planetary rovers

The tracking control and the coordinated allocation control of the planetary rover on soft uneven terrain are rarely addressed at the same time. This paper presents a simultaneous control method of trajectory tracking and coordinated allocation to track the desired trajectory and keep little internal forces. The proposed method consists of two parts: the trajectory tracking controller based on the kinematic model and the coordinated allocation controller based on the dynamic model. In other words, both motion information and force information are used. By rewritten the kinematic model, an improved linear active disturbances rejection control (ILADRC) controller is designed to decrease the longitudinal and lateral tracking errors caused by slipping and skidding. Then by employing the H2/H∞ controller based on the dynamic model, the rover inputs are obtained, and by solving the QP problem using the active-set method, the rover inputs are allocated to each wheel to decrease the internal forces. Based on the wheel-terrain mechanics, the force tracking controller in speed mode is designed using the ILADRC. The final control inputs are the weighted sum of these two angular velocities inputs. Experimental results demonstrate that the controller can decrease the internal forces between wheels on the same side by at least 60%, yet with satisfactory tracking performance.

Wheels' performance of Mars exploration rovers: Experimental study from the perspective of terramechanics and structural mechanics

The soft ground and stones on the surface of Mars may cause sinkage of and damage to the wheels of a Mars rover. Therefore, we analyzed the performance of a wheel-step Mars rover from the perspective of terramechanics and structural mechanics. Using China’s Mars rover wheel prototype and wheel-soil interaction testbed, we obtained the driving performance of the wheels of a Mars rover under various conditions, including full skidding conditions. The vertical load set in the tests was determined using the gravity of Mars and the mass of the wheel-step Mars rover. The results indicate that the driving torque, sinkage, and resistance coefficient have a linear relationship with the wheel vertical load. An analysis of the structural mechanical characteristics of the wheel of the Mars rover was conducted by testing the radial, axial, torsional, and deflection stiffness. We found that the wheel ribs can improve the stiffness of the wheel but may reduce its driving performance. The analysis methods and evaluation indices can be used to analyze the performance of the wheels of other Mars rovers. Furthermore, the findings of this study can be used to optimize wheel design and motion control of wheel-step Mars exploration rovers.

“CloudStation:” A Cloud-Based Ground Control Station for Drones

This article demonstrates an open source cloud-based ground control station that allows remote piloting of drones (aerial-, land-, or sea-based vehicle) from anywhere in the world with just a Web browser. A standard client–server architecture is used for pilot–server and drone–server communication and it is designed to be scalable for the control of millions of drones simultaneously. CloudStation, a proof of concept Web app, is built with Django and hosted on a cloud-based service provider with global availability and scalability. A demonstration from two antipode points (separated around the world) shows the cloud-based command and control of a remote rover.

Improving engineering models of terramechanics for planetary exploration

Abstract This short letter proposes more consolidated explicit solutions for the forces and torques acting on typical rover wheels, that can be used as a method to determine their average mobility characteristics in planetary soils. The closed loop solutions stand in one of the verified methods, but at difference of the previous, observables are decoupled requiring a less amount of physical parameters to measure. As a result, we show that with knowledge of terrain properties, wheel driving performance rely in a single observable only. Because of their generality, the formulated equations established here can have further implications in autonomy and control of rovers or planetary soil characterization.

AADL+: a simulation-based methodology for cyber-physical systems

AADL (architecture analysis and design language) concentrates on the modeling and analysis of application system architectures. It is quite popular for its simple syntax, powerful functionality and extensibility and has been widely applied in embedded systems for its advantage. However, it is not enough for AADL to model cyber-physical systems (CPS) mainly because it cannot be used to model the continuous dynamic behaviors. This paper proposes an approach to construct a new sublanguage of AADL called AADL+, to facilitate the modeling of not only the discrete and continuous behavior of CPS, but also interaction between cyber components and physical components. The syntax and semantics of the sublanguage are provided to describe the behaviors of the systems. What’s more, we develop a plug-in to OSATE (open-source AADL tool environment) for the modeling of CPS. And the plug-in supports syntax checking and simulation of the system model through linking with modelica. Finally, the AADL+ annex is successfully applied to model a lunar rover control system.

A multi-mode real-time terrain parameter estimation method for wheeled motion control of mobile robots

Abstract For motion control of wheeled planetary rovers traversing on deformable terrain, real-time terrain parameter estimation is critical in modeling the wheel-terrain interaction and compensating the effect of wheel slipping. A multi-mode real-time estimation method is proposed in this paper to achieve accurate terrain parameter estimation. The proposed method is composed of an inner layer for real-time filtering and an outer layer for online update. In the inner layer, sinkage exponent and internal frictional angle, which have higher sensitivity than that of the other terrain parameters to wheel-terrain interaction forces, are estimated in real time by using an adaptive robust extended Kalman filter (AREKF), whereas the other parameters are fixed with nominal values. The inner layer result can help synthesize the current wheel-terrain contact forces with adequate precision, but has limited prediction capability for time-variable wheel slipping. To improve estimation accuracy of the result from the inner layer, an outer layer based on recursive Gauss-Newton (RGN) algorithm is introduced to refine the result of real-time filtering according to the innovation contained in the history data. With the two-layer structure, the proposed method can work in three fundamental estimation modes: EKF, REKF and RGN, making the method applicable for flat, rough and non-uniform terrains. Simulations have demonstrated the effectiveness of the proposed method under three terrain types, showing the advantages of introducing the two-layer structure.

Four-wheel Rover’s Motion Control and Modeling Method

The control and modeling problem of four-wheel rover is studied under lunar soft soil and low gravity. The Newton - Euler dynamic model of the four-wheel rover is established by constructing the D-H coordinate system of the rover and gets the value of the wheel angular velocity, and the steering angle is determined by the method of non-holonomic constraints. A closed-loop motion control system for linear velocity and angular velocity feedback regulation of rover is designed and realized by combining the model of wheel terrain mechanics. The experimental results show that the dynamic characteristics of the rover in the process of cruise and the designed motion control system can effectively reduce the disturbance of the external terrain environment and realize the tracking control of the rover linear velocity and angular velocity.

不整地の検出と回避を考慮した惑星探査ローバの誘導制御

不整地の検出と回避を考慮した惑星探査ローバの誘導制御

Design, Control, and Experimentation of Internally‐Actuated Rovers for the Exploration of Low‐gravity Planetary Bodies

This paper discusses the design, control, and experimentation of internally‐actuated rovers for the exploration of low‐gravity (micro‐g to milli‐g) planetary bodies, such as asteroids, comets, or small moons. The rover is actuated by spinning three internal flywheels, which allows all subsystems to be packaged in one sealed enclosure and enables the platform to be minimalistic, thereby reducing its cost. By controlling the spin rate of the flywheels, the rover can achieve large surface coverage by attitude‐controlled hops, fine mobility by tumbling, and coarse instrument pointing by changing the orientation relative to the ground. We first discuss the dynamics of such rovers, their control, and key design features (e.g., flywheel shape and orientation, geometry of external spikes, and system engineering aspects). We then discuss the design and control of a first‐of‐a‐kind test bed that enables the accurate emulation of a microgravity environment for mobility experiments, which consists of a three‐degree‐of‐freedom gimbal attached to an actively controlled gantry crane. Finally, we present experimental results on the test bed that provide key insights for rover control and validate our theoretical analysis.

The aerospace vehicle control characterizing by considerable time delay

In this paper, we propose to compensate the time delay in the vehicle response by a display that demonstrates the vector of predictive velocity projected on the surface located on a preliminary defined distance from the operator’s eyes. The effectiveness of the approach is demonstrated for the tasks of lunar rover docking and control.

Three-layer intelligence of planetary exploration wheeled mobile robots: Robint, virtint, and humint

The great success of the Sojourner rover in the Mars Pathfinder mission set off a global upsurge of planetary exploration with autonomous wheeled mobile robots (WMRs), or rovers. Planetary WMRs are among the most intelligent space systems that combine robotic intelligence (robint), virtual intelligence (virtint), and human intelligence (humint) synergetically. This article extends the architecture of the three-layer intelligence stemming from successful Mars rovers and related technologies in order to support the R&D of future tele-operated robotic systems. Double-layer human-machine interfaces are suggested to support the integration of humint from scientists and engineers through supervisory (Mars rovers) or three-dimensional (3D) predictive direct tele-operation (lunar rovers). The concept of multilevel autonomy to realize robint, in particular, the Coupled-Layer Architecture for Robotic Autonomy developed for Mars rovers, is introduced. The challenging issues of intelligent perception (proprioception and exteroception), navigation, and motion control of rovers are discussed, where the terrains’ mechanical properties and wheel-terrain interaction mechanics are considered to be key. Double-level virtual simulation architecture to realize virtint is proposed. Key technologies of virtint are summarized: virtual planetary terrain modeling, virtual intelligent rover, and wheel-terrain interaction mechanics. This generalized three-layer intelligence framework is also applicable to other systems that require human intervention, such as space robotic arms, robonauts, unmanned deep-sea vehicles, and rescue robots, particularly when there is considerable time delay.

Design and Implementation of Rover Controller and Music Player Control using Sixth Sense Technology

Design and Implementation of Rover Controller and Music Player Control using Sixth Sense Technology

Modelling and Control Design of Rover Vehicle Using Classic and Adaptive Control

This paper presents the dynamics and control of a small-scale rover using custom-built frame, off-the-shelf avionics, motors and batteries. The modeling part incorporates the rotors dynamics and its motion. The modeling process includes analytical equations and experimental identification of different parameters which is difficult to be estimated analytically. The control part incorporates PD controller. A simulator of the complete system was built using Matlab and Simulink. The control code was written in C and was implemented in a PIC microcontroller. A prototype was built and tested with the selected controller to show good stabilization and good matching with the simulator.