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The dynamic behavior of the mechanism is subject to the influence of the clearance in the joints. Existing methods for improving the mechanism's performance usually focus on one type of clearance joint, ignoring the interaction among multiple different types of clearance joints. To address this gap, an optimization method is proposed to lower adverse impact forces and vibrations in planar conjugate cam linkage mechanisms with cam and revolute clearance joints. The contact force model of the clearance joint is formulated using the Flores contact force model and the modified Coulomb friction model. Based on these models and Lagrange's equation of the first kind, the dynamic equations of the mechanism describe its behavior during operation. The optimization method is aimed at minimizing the peak of the mechanism's maximum absolute acceleration by employing the whale optimization algorithm (WOA) to optimize the length of the linkages and the initial angles between them. Additionally, the slider stroke serves as a constraint function. Finally, the effectiveness of the approach is validated using an example of a planar conjugate cam linkage mechanism. Simulation results show a reduction of 65.8% in acceleration peaks and 64.2% in the clearance revolute joint maximum contact force. [ABSTRACT FROM AUTHOR]

We introduce a novel numerical method for the simulation of soft granular materials, in which the particles can undergo large strains under load without rupture. The proposed approach combines an explicit total Lagrangian formulation of Material Point Method (TLMPM) with the Contact Dynamics (CD) method. The TLMPM resolves particle bulk deformations whereas the CD treats contact interactions between soft particles. The efficiency and accuracy of this approach are illustrated by analyzing diametral compression of a soft circular particle and the compaction of an assembly of soft particles up to very high levels of packing fraction. We show that although the assembly undergoes a jamming transition, the particles continue to rearrange as they get increasingly distorted under load. Interestingly, as the packing fraction increases, a transition occurs to a regime fully governed by particle shape change. The evolution of the global stress as well as the connectivity of the particles as a function of the packing fraction are discussed and a predictive model relating stress to packing fraction beyond jamming transition is proposed. [ABSTRACT FROM AUTHOR]

Grain crushing underpins key mechanical behaviours of granular materials. A variety of factors, including grading, particle shapes and loading conditions, have been recognised to affect the crushability of grains and the overall behaviour of a granular material. Among them, the role of intermediate principal stress in a general stress condition on the shear behaviour of crushable granular sand remains less understood, owing to the scarcity of experimental data and analytical tools available. In this paper, a multi-scale computational approach is employed to investigate the shear behaviour of crushable granular sand under general stress conditions with varying intermediate principal stresses and confining pressures. The computational approach features multi-scale coupling between non-smooth contact dynamics and peridynamics, and offers a rigorous way to consider the intertwined evolution of particle size and shape during the process of grain crushing. The numerical study helps to quantify comprehensively and analyse the grain crushing-induced changes of macro- and micro-scale material behaviours including strength, deformability, particle size and shape evolution, particle-scale forces and contact conditions, and the development of anisotropy. The competition between a void-filling mechanism due to grain size change and enhanced friction and interlocking due to grain shape change in dictating the deformation of crushable sand is further discussed. The findings offer insights into the complex behaviours of crushable granular materials under general stress conditions and facilitate future development of physics-based constitutive theories on crushable sand. [ABSTRACT FROM AUTHOR]

We analyse a rigid body in planar motion while touching a rough plane at a finite-sized, circular contact area. Assuming Coulomb friction between the tangential and normal pressure distributions, the resultant forces and torques can be expressed formally with a nonsmooth dependence on the kinematic variables. In the literature, the exact form of the tangential forces is available for special pressure distributions expressed by transcendent functions; recently, an approximate linear model was introduced. Now, we present a nonlinear extension of the approximation, which can be used effectively to characterise slipping-sticking transitions between the bodies. [ABSTRACT FROM AUTHOR]

Recently universal dynamic scaling is observed in several systems, which exhibit a spatiotemporal self-similar scaling behavior, analogous to the spatial scaling near phase transition. The latter one arises from the emergent continuous scaling symmetry. Motivated by this, we investigate the possible relation between the scaling dynamics and the continuous scaling symmetry in this paper. We derive a theorem that the scaling invariance of the quenched Hamiltonian and the initial density matrix can lead to the universal dynamic scaling. It is further demonstrated both in a two-body system analytically and in a many-body system numerically. For the latter one, we calculate the dynamics of quantum gases quenched from the zero interaction to a finite interaction via the non-equilibrium high-temperature virial expansion. A dynamic scaling of the momentum distribution appears in certain momentum-time windows at unitarity as well as in the weak interacting limit. Remarkably, this universal scaling dynamics persists approximately with smaller scaling exponents even if the scaling symmetry is fairly broken. Our findings may offer a new perspective to interpret the related experiments. We also study the Contact dynamics in the BEC–BCS crossover. Surprisingly, the half-way time displays a maximum near unitarity while some damping oscillations occur on the BEC side due to the dimer state, which can be used to detect possible two-body bound states in experiments. [ABSTRACT FROM AUTHOR]

The growing number of space debris is alarming as it threatens space-borne services. Hence, there is an increasing demand to remove space debris to ensure sustainability and protect valuable orbital assets. Over the past few years, the research community, agencies and industries have studied many passive and active debris removal methods. However, the current technology readiness for space debris removal is still low. This paper first presents a comparative study of various space debris removal technologies to address the knowledge gap and quantify the challenges. This paper reviews the current state-of-the-art space technologies relevant to Active Debris Removal (ADR) missions. Detailed trade-off analysis is then presented based on the Low Earth Orbit Pursuit for Active Removal of Debris (LEOPARD) Phase 0-A study; this study is part of the United Kingdom (UK) Space Agency's Active Debris Removal programme. The ADR mission scenario considered in this paper comprises a chaser spacecraft equipped with recommended technologies to capture non-cooperative targets safely. The final capture technology for the LEOPARD mission consists of an active robotic manipulator and a passive net capture mechanism. An analysis of the coupled-body dynamics of the chaser spacecraft carrying the robot manipulator and the targeted debris is carried out in simulation using SimscapeTM. The chaser spacecraft comprises Airbus's Versatile In-Space and Planetary Arm (VISPA) mounted on a base spacecraft from Surrey Satellite Technology Ltd. (SSTL); the targeted debris is SSTL's Tactical Operational Satellite (TOPSAT). The simulation results show dynamic changes in the chaser robot and the target satellite while performing non-cooperative capture. The simulation study accounted for various operational scenarios where the target is stationary or in motion. Further, for different modes of operation, the worst-case end-effector capture force limits were determined using open-loop control to execute a safe capture. Overall, the results presented in the paper advance the current state-of-the-art of robotic ADR and offer a significant leap in designing close-range motion and force control for stabilising the coupled multi-body system during capture and post-capture phases. In summary, this paper pinpoints the technological gaps, identifies barriers to realising ADR missions and offers solutions to catalyse technology maturity for protecting the space ecosystem. [ABSTRACT FROM AUTHOR]

Landing on small-bodies is a very challenging problem that requires high degrees of robustness and autonomy. Being able to perform simulations with great flexibility and accuracy is paramount for the development and design of landing systems. To this end, contact dynamics plays a fundamental role and is often handled by complex tools that require large amount of development and validation efforts and very specific expertise. In the last decade, the Visual Effects (VFX) industry has developed numerous suites that deal with contact dynamics frameworks. In this work, the possibility of leveraging on the work of the VFX industry by using Blender, one of these tools, as the source for the contact dynamics modelling is investigated. This research focuses on the description of the methodology used for the landing simulations and the validation of the tool developed. A step-by-step guide through the simulation setup is given, discussing how the wrapping GNC simulator and Blender interact. Validation tests for the different parameters and dynamic models involved in the simulations are also presented. The results refer to the landing of a CubeSat in the crater region of an asteroid. In particular, the artificial crater that will be generated on Dimorphos by NASA's DART impact in late September 2022, is considered in the simulations presented in this work. Safety maps are generated by post-processing these results, and are used to assess different landing strategies or site-selection criteria on the Dimorphos crater study case. Finally, the role of the developed tool in optimising the use of space resources and its contribution to landing design strategies is discussed. [ABSTRACT FROM AUTHOR]

• A dynamic solver using a linear complementary based approach along with Eulers discretization method. • Simulate the dynamics of a rigid wheel traversing over a flexible beam. • Exact solution of beam and hence the mesh dependency of a finite element solver is removed. • The effect of change in normal gap between and role of frictional force at the wheel beam interface. • The rotation of the wheel and change in contact point between the wheel and beam is evaluated at every time step. This paper proposes a non-linear dynamic solver to simulate the dynamics of a rigid wheel traversing over a flexible beam involving a unilateral contact at the interface. Euler's discretization scheme is extended incorporating Linear Complementary approach to perform explicit integration over time domain. The proposed solver is analytically designed to incorporate frictional force acting at the wheel-beam interface along with the possibility of generation of normal gap between the two bodies. Moreover, rotation of the wheel is also appended in the proposed algorithm and change in contact point between the wheel and beam is evaluated at every time step. After validation with existing literature, the solver is applied to study various dynamic responses of wheel and beam. Further, the technique is applied to moving oscillator model traversing over a flexible beam. The effect of initial wheel velocity, coefficient of friction, frequency of the oscillator on overall dynamic response of beam and wheel have been thoroughly investigated. The proposed algorithm delivers an exact solution based on the system's fundamental mechanics, thus reducing the mesh reliance which amounts to high computational cost in finite element solver. The suggested method provides a broad future potential for solving rigid-flexible contact multibody dynamic problems. [ABSTRACT FROM AUTHOR]

Dynamics modelling and analysis are presented for the flexible threshing mechanism of a grain combine harvester. A detailed model for the contact dynamics between the threshing tooth and grain was developed based on rigid–flexible coupling theory. For the flexible threshing process, a regularisation method for normal contact was based on the Hertz contact theory and nonlinear spring damping, whilst an entropy regularisation smooth approach was introduced to solve the non-differentiable numerical problem for tangential frictional contact. The concept of impact force potential energy was introduced to obtain corresponding generalised impact forces using Lagrange equations. A corresponding computational strategy software was developed in the C programming language. Examples of flexible threshing tooth contact with grains were compared with existing literature analyses to verify the accuracy and efficiency of the proposed algorithm. This approach was implemented as an explicit formulation suitable for improving the global dynamics computational efficiency for threshing systems with frictional impacts. Comparative simulation analyses were performed using commercial discrete element software for a longitudinal flow flexible threshing unit with an ordinary rod–tooth threshing drum. • Contact dynamics of threshing tooth and grain uses rigid–flexible coupling theory. • Introduce impact normal/frictional force potential energy with Lagrange equations. • Entropy regularisation solves normal/frictional contact non-differentiability. • Develop corresponding computational software in the C programming language. • Explicit formulation improves the global dynamics computational efficiency. [ABSTRACT FROM AUTHOR]

The paper describes a general modelling procedure to build a simulation tool to investigate contact motion of a CubeSat on an asteroid surface. We investigate landing performance and landing success for the case of elastic rocky terrain and flat surfaces. As a case study, we focus on the disposal of ESA's Hera Milani CubeSat by landing on the moon of Didymos binary asteroid system. The simulation environment includes the modelling of real shape and 6-DOF motion of the lander, the shape-based gravity models of Didymos and Dimorphos and rocks on surface, that are generated as physical obstacles. Trends and estimates on the performance of the landing phase and the most relevant effects on the outcome of the soil interaction process, are inferred. The statistical results on settling time, dispersion area and motion characteristics, such as number of bounces, show and quantify the effect of rocks on a successful passive and permanent landing. [ABSTRACT FROM AUTHOR]

All mechanical systems behave nonlinearly to a certain extent since there are always reasons for nonlinearities, such as friction and slip effects, in the actual structures. It is important to detect and identify the nonlinearity due to friction and contact in order to investigate their effect on the global behavior of the workpiece-fixture system. That is a prerequisite for modeling the dynamic contact behavior at the interface between the workpiece and clamping elements. In this research, the workpiece-fixture system was excited with a shaker using the swept sine signal. The nonlinearities could be detected by comparing and analyzing the frequency responses of the structures in Bode plots. However, the nonlinearities behaved differently at various frequencies within the observation range. Different mechanisms such as nonlinear stiffness and damping, micro-slip friction, are responsible for that. Then the nonlinear contact behavior at the clamping positions was successfully identified by means of the Hilbert transform. In addition, the clamping force directly influenced the nonlinear stiffness of the workpiece-fixture system. [ABSTRACT FROM AUTHOR]

• A discrete compliant rod model to simulate a compliant touch system is proposed. • The jump of normal contact force and impulse marks the Painlevé paradox happening. • Relative motion modes of contact points as the Painlevé paradox occurs are gained. • Increasing structural compliance expands the parameter region of dynamic jam. • The influence law of compliance on dynamic jam is validated by experiments. Dynamic jam (self-locking) is a controversial problem that can occur in robotic systems with friction. Jam happens if an elongated body is pushed across a rough surface and the friction force is sufficiently large—then friction induces interpenetration at the contact surface. This action has been termed the Painlevé paradox. Various mathematical methods have been developed to analyze the inconsistent equations of rigid body dynamics that represent jam; these are aimed at resolving questions of existence and non-uniqueness. The present paper investigates the physical characteristics of the Painlevé paradox both theoretically and experimentally. Considering tangential contact compliance, an efficient theoretical model is developed to investigate the sliding dynamics of finger compliant touch systems. An event-driven method is adopted to solve the governing equation expressed by generalized coordinates. The results show that the tangential relative motion of a contact pair will be jam rather than slip if the coefficient of friction is sufficiently large, meanwhile the relative motion mode transfers from M 1 —gross slip into M 3 —dynamic jam or M 2 —a transition mode. Structural compliance somewhat enlarges the range of the coefficient of friction which results in jam. This conclusion has also been validated by experiments investigating the Painlevé paradox for two-link manipulators. The analytical approach that results in this new understanding provides an effective tool for designing a soft robotic system made of highly compliant materials. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper proposes an algorithm to solve vehicle–bridge interaction (VBI) problems. It describes the VBI system in a linear second-order differential-algebraic equation (DAE) manner, incorporating the motions of both the vehicle and the bridge subsystems, together with the contact forces. On account of the conjugation between the VBI system's motions and contact forces, the key feature of the proposed algorithm is to solve the DAE with the the algebraic method of elimination by substitution, avoiding the singularity of the differential operator. It enables a versatile and consensus solution scheme for different types of contact mechanisms, including the rigid contact model with constraints, the elastic contact model with the compliance method, and the creep tangential contact model, as well as different wheel–rail profiles. Combined with an appropriate numerical integration scheme, it allows an explicit expression of the contact forces, subsequently leading to the partitioned non-iterative analysis of the motions of both the vehicle and the bridge subsystems. In addition, by incorporating the dynamic condensation of wheels' degrees of freedom into those of upper components in a matrix form, i.e. a reduced system approach, the proposed algorithm can avoid the numerical drift associated with the kinematic constraints on the acceleration level. To demonstrate the accuracy of the proposed approach, this study first examines a benchmark example of a single degree of freedom sprung mass model traversing a simply supported bridge. Further, it considers a more realistic problem of one and eight train vehicles crossing three three-span continuous bridges. The comparisons and the agreements with existing algorithms prove the accuracy and computational efficiency of the proposed analysis scheme. [ABSTRACT FROM AUTHOR]

The pin-in-the-slot joint is a common element in machines, and the dynamics of joints with clearances is an actively investigated topic. Important applications of such a joint can be found in Geneva mechanisms, robotized gear selectors, centrifugal vibration absorbers (CPVA) and other important mechanical devices. The paper will review the main analytical steps required to obtain the equations characterizing the different force contact models. Furthermore, a numerical test bench where such models are introduced for modeling the clearances between the pin and slot is proposed. In this regard, the present study will offer a comparison and discussion of the numerical results obtained with the different force contact models herein reviewed. [ABSTRACT FROM AUTHOR]

Collaborative state recognition is a critical issue for physical human-robot collaboration (PHRC). This paper proposes a contact dynamics-based state recognition method to identify the human-robot collaborative grinding state. The main idea of the proposed approach is to distinguish between the human-robot contact and the robot-environment contact. To achieve this, dynamic models of both these contacts are first established to identify the difference in dynamics between the human-robot contact and the robot-environment contact. Considering the reaction speed required for human-robot collaborative state recognition, feature selections based on Spearman's correlation and random forest recursive feature elimination are conducted to reduce data redundancy and computational burden. Long short-termmemory (LSTM) is then used to construct a collaborative state classifier. Experimental results illustrate that the proposedmethod can achieve a recognition accuracy of 97% in a period of 5ms and 99% in a period of 40 ms. [ABSTRACT FROM AUTHOR]

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Force control provided by a small-scaled free-flying space robot on a floating or spinning target will be required for future on-orbit servicing missions, such as detumbling a target, performing an assembly or a maintenance operation. Regarding to different contact geometries for a space robot interacting with a spinning target, this paper addresses the contact model considering its multi-dimensional characteristics. A hybrid motion and force controller is developed to acquire desired contact forces and space robot configuration despite the floating feature of the system. On this basis, the control strategy to implement the operations of three typical phases, namely approaching phase, contact phase and post-contact phase, is proposed. The simulations have been performed to verify the control approaches and visualize the contact scenarios. • Multi-dimensional contact models regarding to two contact geometries are formulated. • Hybrid motion and force controllers for two contact scenarios are developed. • A novel control strategy for typical on-orbit servicing phases is proposed. • Numerical simulations based on Simscape Multibody verify the approaches. [ABSTRACT FROM AUTHOR]

Smooth approaches are able to model reasonably well contact/impact events between two bodies, showing some peculiarities when dealing with certain geometries and arising certain issues with the detection of the initial instant of contact. The characterization of multiple-simultaneous interaction systems, considering (or not) energy dissipation phenomena (mainly friction), is always an interesting research topic, addressed from different perspectives. In the present work, the process of design, optimization and verification of a multiple-impact, day-to-day multibody novel model is shown. Specifically, we have decided to focus on a pool/billiard game due to its geometry simplicity. The model involves several balls moving freely and rolling, suffering different kinds of contacts/impacts among them and against the cushions and the cloth. In this system, the proper modelling of both contact and friction forces in the multiple, simultaneous contacts and impacts events is critical to obtain consistent results. In addition, these forces are complicated to model because of its nonlinear behaviour. The different existing approaches when dealing with multiple-contact events are briefly described, along with their most distinctive features. Then, the interactions identified on the model are implemented using several nonlinear contact-force models, following a smooth-based approach and considering friction phenomena, aiming at determining the most suitable set of both contact and friction force models for each of these implemented interactions, which take place simultaneously, thus resulting in a complex system with multiple impacts. Subsequently, the solving method that provides the most accurate results at the minimum computational cost is determined by testing a simple shot. Finally, the different interactions on the model are verified using experimental results and previous works. One of the main goals of this work is to show the some of the issues that arise when dealing with multiple-simultaneous impact multibody systems from a smooth-contact approach, and how researchers can deal with them. [ABSTRACT FROM AUTHOR]

We show that Hertzian particle contacts are the underlying cause of the as-yet-unexplained noninteger power laws in weakly nonlinear rheology. In the medium amplitude oscillatory shear (MAOS) region, the cubic scaling of the leading order nonlinear shear stress (σ 3 ∼ γ 0 m 3 , m 3 = 3) is the standard expectation. Expanding on the work by Natalia et al. [J. Rheol. 64, 625–635 (2020)], we report an extensive data set of noncubical, noninteger power law scalings m 3 for particle suspensions in two immiscible fluids with a capillary attractive interaction, known as capillary suspensions. Here, we show that distinct power law exponents are found for the storage and loss moduli and these noninteger scalings occur at every secondary fluid concentration for two different contact angles. These compelling results indicate that the noninteger scalings are related to the underlying microstructure of capillary suspensions. We show that the magnitude of the third harmonic elastic stress scaling m 3 , elastic originates from Hertzian-like contacts in combination with the attractive capillary force. The related third harmonic viscous stress scaling m 3 , viscous is found to be associated with adhesive-controlled friction. These observations, conducted for a wide range of compositions, can help explain previous reports of noninteger scaling for materials involving particle contacts and offers a new opportunity using the variable power law exponent of MAOS rheology to reveal the physics of particle bonds and friction in the rheological response under low deformation instead of at very high shear rates. [ABSTRACT FROM AUTHOR]

This paper presents a new algorithm that approximates the forces that develop between a human hand and the handles of a climbing wall. A hand-to-handle model was developed using this algorithm for the Open Dynamics Engine physics solver, which can be plugged into a full-body climbing simulation to improve results. The model data are based on biomechanical measurements of the average population presented in previously published research. The main objective of this work was to identify maximum forces given hand orientation and force direction with respect to the climbing wall handles. Stated as a nonlinear programming problem, solution was achieved by applying a stochastic Covariance Matrix Adaptation Evolution Strategy (CMA-ES). The algorithm for force approximation works consistently and provides reasonable results when gravity is neglected. However, including gravity results in a number of issues. Since the weight of the hand is small in relation to the hand-to-handle forces, neglecting gravity does not significantly affect the reliability and quality of the solution.

This brief paper emphasizes on the experimental study of a hybrid contact model combining a traditional physical-based contact model and a data-driven error model in order to provide a more accurate description of a contact dynamics phenomenon. The physical-based contact model is employed to describe the known contact physics of a complex contact case, while the data-driven error model, which is an artificial neural network model trained from experimental data using a machine learning technique, is used to represent the inherent unmodeled factors of the contact case. A bouncing ball experiment is designed and performed to validate the model. The hybrid contact model can duplicate experimental results well, which demonstrates the feasibility and accuracy of the presented approach. [ABSTRACT FROM AUTHOR]

The pin-in-the-slot joint is a common element in machines, and the dynamics of joints with clearances is an actively investigated topic. Important applications of such a joint can be found in Geneva mechanisms, robotized gear selectors, centrifugal vibration absorbers (CPVA) and other important mechanical devices. The paper will review the main analytical steps required to obtain the equations characterizing the different force contact models. Furthermore, a numerical test bench where such models are introduced for modeling the clearances between the pin and slot is proposed. In this regard, the present study will offer a comparison and discussion of the numerical results obtained with the different force contact models herein reviewed.

Based on the theory of rigid-flex coupled multi-body system dynamics,systematic research has conducted on transmission system of a coal winning machine’s cutting part. By using the software of Recur Dyn,the model was established including transmission gears,drive shaft and bearing. Considering the flexible characteristics of drive shaft,the rigid-flexible coupled model was built.Transmission system of a coal winning machine’s cutting part was simulated dynamics analysis before contact parameter setting on the parts of transmission system. The working process of shearer transmission system was described intuitively and dynamically. Results showed that 11 th gear mesh together is the biggest,11272634. 4 N.4 th. The maximum strain,measured at the axes of 4,is 0. 081. It reveals the difference of Gear meshing force curve and its frequency-domain information between Rigid-flexible coupling system and Stiff systems. Results provide a basis for optimum design of the transmission system and prediction of fatigue life.

In this paper,the research of the scraper conveyor is carried out,the force analysis of the adjacent middle pan group and the dumbbell pin is carried out,and the dumbbell pin load data is obtained by the dumbbell pin load test system. The ANSYS/ls-dyna software is used to simulate the nonlinear contact dynamics of the middle pan group and the dumbbell pin under the push-slip condition of the scraper conveyor. The contact stress of the dumbbell pin is the largest,and the maximum contact stress of the dumbbell pin occurs at the abrupt change of the dumbbell pin section,and the maximum contact stress of the dumbbell pin And the contact stress concentration between the two middle slots occurred at the joints of the dumbbell pin and the middle ditch. The simulation results were in accordance with the actual working conditions. This study provides a dumbbell pin load test program,and through the test simulation to verify its correctness and feasibility,while the middle slot and dumbbell pin structure size optimization method.

In industry, the capability to predict the tool point frequency response function (FRF) is an essential matter in order to ensure the stability of cutting processes. Fast and accurate identification of contact parameters in spindle-holder-tool assemblies is very important issue in machining dynamics analysis. This work is an attempt to illustrate the utility of soft computing techniques in identification and prediction contact parameters of spindle-holder-tool assemblies. In this paper, three soft computing techniques, namely, genetic algorithm (GA), simulated annealing (SA), and particle swarm optimization (PSO) were used for identification of contact dynamics in spindle-holder-tool assemblies. In order to verify the proposed identification approaches, numerical and experimental analysis of the spindle-holder-tool assembly was carried out and the results are presented. Finally, a model based on the adaptive neural fuzzy inference system (ANFIS) was used to predict the dynamical contact parameters at the holder-tool interface of a spindle-holder-tool assembly. Accuracy and performance of the ANFIS model has been found to be satisfactory while validated with experimental results. [ABSTRACT FROM AUTHOR]

Traditional physics-based contact models have been widely used for describing various contact phenomena such as robotic grasping and assembly. However, difficulties in carrying out contact parameter identification as well as the relatively low measurement accuracy due to complex contact geometry and surface uncertainties are the limiting factors of the physics-based contact modeling methods. In this paper, we present a novel hybrid contact modeling (HCM) method as an endeavor to discover models that can more accurately simulate practical contact scenarios than traditional physics-based contact models. The proposed method is implemented by combining a physics-based contact model and a data-driven error model. This approach is validated by using simulations of a bouncing ball, a flat-shot, and a three-dimensional (3D) peg-in-hole. The results demonstrate the feasibility and consistent performance of the HCM method. [ABSTRACT FROM AUTHOR]

• Allowable range of contact between tethered nets and debris for debris capture is studied. • Oriented Bounding Box (OBB) is used to reduce computation time for collision detection. • Success of capture depends on net position deviation, ejection velocity and distance to debris. This study focused on the robustness of tether net in capturing space debris and investigated the effect of ejection alignment on capture success, with an assumption that there was an alignment between net ejection direction and direction to debris. The robustness of capture was significantly affected by the distance to the debris and the deployed size of the tether net at the timing of collision with the debris. [ABSTRACT FROM AUTHOR]

This paper presents a new algorithm that approximates the forces that develop between a human hand and the handles of a climbing wall. A hand-to-handle model was developed using this algorithm for the Open Dynamics Engine physics solver, which can be plugged into a full-body climbing simulation to improve results. The model data are based on biomechanical measurements of the average population presented in previously published research. The main objective of this work was to identify maximum forces given hand orientation and force direction with respect to the climbing wall handles. Stated as a nonlinear programming problem, solution was achieved by applying a stochastic Covariance Matrix Adaptation Evolution Strategy (CMA-ES). The algorithm for force approximation works consistently and provides reasonable results when gravity is neglected. However, including gravity results in a number of issues. Since the weight of the hand is small in relation to the handto- handle forces, neglecting gravity does not significantly affect the reliability and quality of the solution. [ABSTRACT FROM AUTHOR]

The dynamic characteristics of thin-walled four-point contact ball bearing with crown-type cage are important to the dynamic performance and motion accuracy of an industrial robot. Considering multi-clearances, dynamic contact and impact relationships of the ball, ring raceway and crown-type cage, a general methodology for dynamic simulation analysis of the bearing is investigated in the proposed work. In accordance with the geometry of torus, the geometric equation of accurate ring raceway is derived and integrated into the three-dimensional ring raceway using user's subroutines. The parameterized and assembled three-dimensional model of the bearing is established using ADAMS's macro-programs. Applying a penalty formulation and a unilateral nonlinear spring–damper model to the bearing, the internal contact interaction is represented as the compliant contact force model using IMPACT function. The multibody contact dynamic models of the bearing are solved by HHT algorithm with ADAMS/Solver. The dynamic results of the contact force, impact force and motion stability of the bearing are discussed under the condition of different loads. The static load distribution and cage's angular velocity of simulation model are verified by the theoretical values. The motion trajectory of outer ring's center is circular with a whirling motion. The sphere-to-partial torus surface contacts (ball–racetrack contact) are always four contact points in the load zone of the bearing. Applying pure radial load or rotating radial load, the impact force of ball-to-cage small pocket contact is much larger than that of radial and axial load combination in the non-load zone of the bearing. As a result of the large impact force of ball-to-cage small pocket contact, the angular velocities of the ball and cage are varying greatly in the non-load zone. The impact force of ball-to-cage big pocket contact is very small. The angular velocity of the ball is always that of pure rolling in the load zone and varying slightly in the non-load zone. The new method can be applied to investigate dynamic analysis and design of high-precision industrial robots with multi-clearances, multi-ball bearings under complex, time-varying working conditions. [ABSTRACT FROM AUTHOR]

A unifying slipping and sticking frictional impact model for multibody systems in contact with a frictional surface is presented. It is shown that the model can lead to energetic consistency in both slip and stick states upon imposing specific constraints on the coefficient of friction (CoF) and the coefficient of restitution (CoR). A discriminator in the form of a quadratic function of the pre-impact velocity is introduced based on an isotropic Coulomb constraint such that its sign determines whether the impact occurs in the sticking mode or in the slipping mode just prior to the contact. Solving for the zero-crossings of such a function in terms of the CoF and the CoR variables leads to another discriminator called Critical CoF, which is the lowest static CoF required to prevent the subsequent impulse vector violating the isotropic friction cone constraint. Investigating conditions for the energetically consistent impact model reveals that the maximum values of either CoR or CoF should be limited depending on the stick or slip state. Furthermore, it is shown that these upper-bound limits in conjunction with the introduced Critical CoF variable can be used to specify the admissible set of CoR and CoF parameters, which can be represented by two distinct regions in the plane of CoF versus CoR. Finally, a case study using the Kane's example for impact in an MBS involving frictional impacts occurring in both slip and stick states are presented to support the analytical results. [ABSTRACT FROM AUTHOR]

Erosion processes and the associated static/flowing transition in granular flows are still poorly understood despite their crucial role in natural hazards such as landslides and debris flows. Continuum models do not yet adequately reproduce the observed increase of runout distance of granular flows on erodible beds or the development of waves at the bed/flow interface. Discrete Element Methods, which simulate each grain's motion and their complex interactions, provide a unique tool to investigate these processes numerically. Among them, Convex Methods (CM), resulting from the convexification of Contact Dynamics methods, benefit from a robust theoretical framework, ensuring the convergence of the numerical solution at every time iteration. They are also intrinsically more stable than classical Molecular Dynamics methods. However, although already implemented in engineering fields, CMs have not yet been tested in the framework of flows on erodible beds. We present here a Convex Optimization Contact Dynamics (COCD) method and prove that it generates a numerical solution verifying Coulomb's law at each contact and iteration. After its calibration and validation with experiments and another widely used Contact Dynamics method, we show that our simulations accurately reproduce qualitative and even many quantitative characteristics of experimental granular flows on erodible beds, including the increase of runout distance with the thickness of the erodible bed, the change of the static/flowing interface and the presence of erosion waves behind the flow front. Beyond erosion processes, our article endorses CMs as potential accurate tools for exploring complex granular mechanisms. • The method COCD is based on an implicit scheme and large time step values are used. • The computational efficiency of COCD is derived from existing convex solvers. • Simulations of granular flows are compared to laboratory scale experiments. • COCD reproduces the complex interaction between the flow and the erodible layer. • Convex methods are relevant for the simulation of complex granular flow processes. [ABSTRACT FROM AUTHOR]

We are proposing Tulczyjew’s triple for contact dynamics. The most important ingredients of the triple, namely symplectic diffeomorphisms, special symplectic manifolds, and Morse families, are generalized to the contact framework. These geometries permit us to determine so-called generating family (obtained by merging a special contact manifold and a Morse family) for a Legendrian submanifold. Contact Hamiltonian and Lagrangian Dynamics are recast as Legendrian submanifolds of the tangent contact manifold. In this picture, the Legendre transformation is determined to be a passage between two different generators of the same Legendrian submanifold. A variant of contact Tulczyjew’s triple is constructed for evolution contact dynamics.