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Position control of the mechanical structure with naturally limited stiffness is a common problem. Moreover, the system is usually exposed to random exciting by the external force effects and yet it is needed to hold the system in the desired position. Such an example in engineering practice can be the machine tool quill slim structure, which determines the machining accuracy and the machined surface quality. The limited structure stiffness can be overcome by suitable support structure solution. In principle, it is a matter of introducing the necessary force effect in the place where it is necessary to ensure the required position. A promising means how to apply control force to the flexible structure tip can be a thin cable structure with the force actuation and proper force control. The resulting system is characterized by increased stiffness achieved in a mechatronic manner. Therefore, the introduced concept is called mechatronic stiffness. The article describes selected mechanical arrangement of the mechatronic stiffness concept, its features, behaviour and control results. The proposed approach offers a solution for precise position control of the flexible structure. An experimental device was created in parallel with the simulation experiment and preliminary simulation results are obtained. The described concept is transferable to other flexible structures such as various manipulators.

Undesired vibration is a common issue when dealing with manufacturing machines, especially when dealing with thin structures. To decrease the external disturbance sensitivity of such systems, represented for example by machine tool quill, the auxiliary cable structure is attached to the system. The auxiliary cable structure increases system damping and decreases undesired structure vibrations by the passive or active way, depending on the deployment and purpose. In this article, cables are attached to the end-effector to suppress undesired vibrations and related experimental stand is prepared. Experimental stand parameters are identified using least square method. The control strategy using pole placement is presented and its suitability is verified using external disturbance force. The frequency analysis shows the promising behaviour of controlled cable structure attached to the original system as well as the experimental results.

The paper deals with the creation and implementation of a methodology for optimizing the parameters of cascade control of the machine tool axis drives. The first part presents the identification of a dynamic model of the axis based on experimental data from measuring the axis dynamics. The second part describes the controller model, selection of optimization objective functions, and optimization of constraint conditions. The optimization of controllers is tuned by simulation using identified state-space model. Subsequently, the optimization procedure is implemented on the identified model, and the found control parameters are used on a real machine tool linear axis with different loads. The implementation of the proposed complex procedure on a real horizontal machine tool proved the advantage of simultaneous tuning of all parameters using optimization methods. The strategy solves the problem of mutual interaction of all control law parameters disabling effective usability of gradual sequential tuning. The methodology was developed on a speed control loop, the tuning of which is usually the most difficult due to the close interaction with the dynamic properties of the machine mechanics. The whole procedure is also applicable to the position and current control loop.

This paper discusses a postprocessor for milling robots connected to additional linear machine axes where toolpath is optimized with respect to variable properties of the robot in its workspace. A toolpath optimization method is proposed based on an experimentally verifiedrobot stiffness model. After postprocessor distribution of the movements between the robot and the linear axes, the collision states during machiningcannot be verified in common CAM. Therefore, a solution enabling simulation of movements after optimization is proposed. The tool center point coordinates are used to control the robot and additional machine axes, while the joint coordinates calculated by inverse kinematic transformation are used to verify the movements.

The concept of wave-based control (WBC) has been around for about two decades. It is designed primarily for controlling the end-point motions of one-dimensional lumped mass flexible chains. The systems under consideration are, therefore, severely underactuated. Typical control objective for such systems is a point-to-point motion without unwanted residual oscillations. These oscillations, however, become troublesome especially for the lightly damped cases. The only way to attenuate them is to ‘shape’ the control input. For this WBC concept considers a set of hypothetical (forward and backward) motion waves, which combine to form the actual motions. This document critically investigates wonderful properties of WBC which are claimed over the years and presents a completely new mathematical and rigorous treatment of the method. We rectify several misconceptions, especially on the level of a priori knowledge which is required on the system dynamics. Second, the authors present a novel step-by-step procedure to design a WBC law which ultimately leads to a number of opportunities for future explorations. Finally, the necessary and sufficient conditions in system parameter space for the stability of WBC are rigorously elucidated for the first time in the literature to the best of our knowledge.

The fast and precise positioning of flexible mechanical structures is often corrupted by the unwanted dynamics in the form of a residual vibration. Therefore, we would like to find an appropriate control strategy that is capable to suppress this effect. The control strategies can be basically divided into two main groups: feedback control and feedforward control. The feedback control with the information from integrated sensors is capable to ensure the stability and robustness, but it may require large actuator effort, and it may be difficult to design satisfactory controllers for rapid movements. The feedforward methods including command/input shaping are based on the model of the system and usually require no additional sensors. They can significantly eliminate residual vibration, but feedforward methods cannot deal with disturbances, and the quality of their performance is strongly determined by the precision of the used model on which they are based. This paper proposes the novel solution to these problems, the so-called SHAVO (SHAper $$+$$ serVO control) strategy that combines advantages of both approaches. Compared to other methods combining command shaping and feedback controller, the SHAVO approach differs in two key features. Firstly, it uses a different structure, the model of the system is used not only for shaper synthesis but also for predicting system outputs and states. Secondly, the shaper itself is highly optimized with arbitrary adjustable time length, not an impulse series, not limited by the system’s natural frequency.

Pointing consists in orienting a line OP of a rigid body, with its point O fixed, P mobile. The operation can thus be achieved in two steps, one to provide P with the desired longitude on the sphere centered at O, of radius OP ¯ , the other to provide P with the desired latitude. While this operation is simpler than a full rigid-body rotation, its kinematics is not yet fully recorded in the literature. In fact, the kinematics of pointing cannot be considered as being included in the kinematics of spherical motion, because the latter is known to form a Lie group, while pointing operations do not. This paper is an effort to shed light on the kinematics of pointing by means of the visualization of the workspace of the mechanism used for its realization. In doing this, a strategy is proposed for the planning of pointing trajectories using a three-revolute spherical wrist. The contributions proposed by the authors thus target the workspace visualization and the path-planning of three-axis wrists when used for pointing operations.

Vibration and ride comfort is usually evaluated for vehicle passengers in passive state, in particular the human passenger is considered as a passive mechanical system. However, several experiments and experience with them indicated that the human passenger is an active participant of the dynamic process of comfort creation. This paper builds on these results with the novelty that the ultimate consequence of human muscle tension change is the improvement of ride comfort impression. Multibody model of human passenger body was developed and calibrated based on carried out experiments. The activity of passenger body is modeled as its muscle tension. The positive influence of muscle tension level on vibration and ride comfort is evaluated. It corresponds to the measured activities of human passenger bodies during carried out experiments.

An interesting concept of wave-based control(WBC) has been around for about two decades now. Its core objective is to control the end-point motions of 1-D lumped mass flexible chains using one single base actuator and a motion sensor from the immediately adjacent mass. This severely underactuated mechanism is shown to achieve a benchmark point-to-point motion without (or with considerably attenuated) residual oscillations. WBC strategy is based on a set of hypothetical motion waves (in forward and backward directions) as the decomposition of physical motion of the masses. This paper revisits the concept in order to rectify several misconceptions, especially the earlier claim that such a control strategy can be created without any prior knowledge on the system dynamics. In particular the stability of the controlled system is revisited. Furthermore we offer one well-defined step-by-step procedures for formulating a WBC law and suggest vast opportunities for future explorations. An example parametric optimization pathway is also presented.

The motivation for this work is the control of flexible mechanical systems, specifically their position control without residual vibrations. The actuators are attempting to position the “important point” at the far end of the flexible system through wave based control to eliminate the vibrations at the end of the motion. The synchronous electric generator is modelled as flexible mechanical system. The wave-based control method is presented. The paper shows how to compute and use the “launch” and “reflected” waves for control. If appropriate strategy is used, the flexible system will be displaced to the required position with no residual vibrations. If the superposition principle is valid, various motions can be controlled simultaneously. The state feedback control is shown for comparison.

The paper deals with the modeling and control of redundantly actuated parallel mechanisms. The redundant actuation means the redundant number of actuators, that is, more actuators than degrees of freedom of the mechanism. These machines bring the possibility of removing the backlash by the so-called antibacklash control. However, control of such a structure suffers from several new control problems like the danger of mutual fighting of the redundant actuators. This is especially problematic if the geometric imperfections appear. The presented solution is based on the usage of robust sliding mode control for uncertain dynamics. The paper explains classic approach of sliding mode control and its new modification based on the uniform usage of all actuators replaced by the fictitious auxiliary drives. The verification of the proposed algorithms is presented by two planar mechanisms with four actuators and three degrees of freedom. The first one is the fiber-driven mechanism, and the second one is the rigid 4RRR mechanism “Crosshead.”

The article deals with the usage of methods of learning algorithms of neural networks for solving of collision states problem within multi-robotic cooperation. Nowadays, multi-robotic cooperation is a highly used method of work of two or more industrial robots. The requirements for elimination of collision states are getting more difficult when the multi-robotic system is more complicated. Methods of neural networks provide suitable tools for solving of complex cooperating problems. In the beginning of the article, we discuss the term “collision state” and the possibilities of its solving. In the following chapter, we discuss the theory of neural networks and learning algorithms, which we applied in solving of the collision states. In the final chapter, we implemented the practical verification of the model neural network in JSNN programme. It consisted of creating and learning of the training data and subsequent verification of the test data.

This article discusses the application of the Hirose ́s function for the achievement of the serpentine locomotion of the snake-like robot. Verification of the accuracy of locomotion was performed by simulation in the MATLAB 2012a program. At the beginning of the article, the biological aspects and the principle of the snake’s locomotion are mentioned. In the following chapter, the basic Hirose ́s function, which is subsequently transformed into the discreet shape in the Cartesian coordinates, is described. Moreover, relations for the calculation of rotation angle of the individual segments, wrapping angle and other similar parameters have been obtained. At the end of the article, simulations have been performed within which the influence of changes of the individual parameters of the function on the change of the shape of the snake-like robot have been observed.

SUMMARYThe paper deals with the development and application of a new adaptive calibration method that extends the geometrical calibration of mechanisms from calibration of only dimensions and kinematical joint positions into the calibration of kinematic joint shape imperfections. Originally unknown nonlinear properties of the kinematical pairs are adaptively included into the kinematical models that are used during the calibration calculation. The method uses description by local linear models and validity functions in order to identify and describe nonlinear properties of the kinematical pairs. During each calibration step, various models with growing complexity are considered before the best model variant is selected to improve calibration results. The method is mainly devoted to the structures with many loops like parallel and fiber-driven parallel mechanisms. The method is applied to parallel mechanism Sliding Star and parallel fiber-driven mechanism Quadrosphere.

This article proposes an alternative optimization framework applied to topology optimization of modular lightweight cabled-truss structures. These structures are described as a system of intrinsically positioned cables and triangular bar formations jointed at their ends by hinged connections to form a rigid framework. The optimized topologies are determined through a stochastic discrete optimization procedure that uses ground structure approach, nonlinear finite element analysis, and quantum-inspired evolutionary algorithms. The optimization searches for optimal mass reduction with minimal losses in stiffness, such relation, is expressed by the stiffness-to-mass ratio parameter. Nonlinear finite element analysis is used to evaluate the static structural response. In order to decrease computation time, kinematically instable and structurally invalid individuals are filtered before evaluation. Modular design approach is taken into consideration to reduce the number of design variables and increase the produ...

In this article we are discussing the suggestion of planning maintenance in such situation that we have failures in database of failures and maintenance registered also according to type of failure— priority or non-priority. We are assuming that maintenance must be mainly oriented on avoiding major failures of machines. The effect of maintenance manifests with delay and is dependent on development of failures. We express this problem as linear programming task that is solvable with Solver-extension of application Excel. We demonstrate the suggested solution on example of failures of machines between years 2010 and 2012.

This paper proposes cabled-trusses benchmarks for mechanical engineering applications and provides suitable tools for modeling and optimization of cabled-trusses. These structures correspond to a system of cables and triangular bar formations jointed at their ends by hinged connections to form a rigid framework. The optimized cabled-truss is determined through a discrete optimization procedure that uses nonlinear finite element analysis, genetic algorithm, and fuzzy logic. In this work, planar and spatial trusses and cabled-trusses are optimized to achieve minimum weight designs. Also, the structural performance of the optimized structures is compared. In summary, the results show that cabled-trusses feature improvements over trusses.

The paper deals with the design of optimized input shapers for non-vibrational control of flexible mechatronic systems. The described method is based on a combination of advantages from two approaches – precomputed control curves and on-line shapers. The strategy has two steps. Primarily, an optimized precomputed curve is found as a solution to the point-to-point control problem with respect to any requested optimization goals. Then it is transformed into an on-line shaper with the re-entry property. The resulting shaper transforms any arbitrary input signal to a non-vibrational one. In contrast to other techniques, the shaper length is not determined from the system natural frequency. The shaper can be easily modified with respect to position, velocity, acceleration or jerk control. The theoretical results are verified by experiments using a laboratory crane.

This paper presents a model of the interaction of mating gears. The approach uses 3D gear geometry for the calculation of teeth penetration. The contact force is evaluated using the penetration between all mating teeth and the known contact stiffness. Gear meshing is evaluated using an analytical solution based on gear flank parameterization. The advantage of such an approach is to involve real gear geometry in the calculation of the contact force. The model involves the effects of the backlash between teeth (gear rattling, hammering), engagement and disengagement of the teeth pair in contact and the variation of the number of teeth pairs in contact (gear whine). The ideal tooth flank geometry is modified using the measured flank modifications. The dynamic behaviour of the interaction between two gears is modelled and compared with the 2D spring-damper model.DOI: http://dx.doi.org/10.5755/j01.mech.23.3.14325

The paper deals with the multibody system software which implements the solution of the global dynamic problem for multibody systems described by redundant coordinates (DAE equations) and with a possibility of redundant number of actuators. The aim of the global dynamics evaluation is mainly the machine synthesis. The necessity of such formulation arises especially in robotics where the accessible velocities and accelerations on the given trajectory are important for the motion planning and for the design optimization of robots and manipulators. The analogical problem can be very important also for the design of any other machine type. The developed software is therefore one of the important tools for the multiobjective machine synthesis.

Experimental measurements focused on the investigation of a fibre behaviour are performed on an assembled weigh-fibre-pulley-drive mechanical system. The fibre is driven with one drive and is led over a pulley. On its other end there is a prism-shaped steel weight, which moves in prismatic linkage on an inclined plane. The angle of inclination of the inclined plane could be changed. The position of the weight is asymmetric with respect to the vertical plane of drive-pulley symmetry. Drive exciting signals can be of a rectangular, a trapezoidal and a quasi-sinusoidal shape and there is a possibility of variation of a signal rate. Dynamic responses of the weight and the fibre (time histories of the weight position, of the drive position and of the force acting in the fibre) are measured. The same system is numerically investigated by means of a multibody model. The influence of the model parameters on the coincidence of results of experimental measurements and the simulations results are evaluated. The simulations aim is to create a phenomenological model of a fibre, which will be utilizable in fibre modelling in the case of more complicated mechanical or mechatronic systems.

Typically single-mass absorbers combat a single excitation frequency at a time. In this paper we explore a novel control scheme to handle multiple and time-varying frequencies, but again using a single-mass absorber. The key scientific contribution is in the new way the spectral sensitivity is induced to the absorber substructure at multiple frequencies. This tuning process is achieved using a novel extension to the conventional Delayed Resonator (DR) concept with several delays. We show that the method can track all frequencies in real time. Therefore the new conception dramatically expands the traditional fixed-frequency absorption operations, for instance Dual Frequency Fixed Delayed Resonator (DFFDR). On-line deployment starts with a selection of a base delay in the feedback control on a given passive absorber. Necessary feedback gains for proper tuning are evaluated and control decision is made in real time. The stability repercussions of this control law, however, need to be assessed in advance. For this we use a recent characteristic root approximation method, QPmR (Quasi-Polynomial Mapping Based Root finding). These assessments create some restrictions for tunable frequency ranges with guaranteed stability. Such limitations, as well as the practical complexities of the new tuning method are also discussed over an example case study.

The paper deals with the simulation of a concept performing the deformation measurement of a serial robot. The simulation model consist of two parts. The one of them is the model of the flexible robot with the flexibility concentrated in its gearboxes and its beams. The other one is the model of sensors measuring virtually the flexible deformations of the gearboxes and the arms. The rotary encoders are used for the gearboxes and the sensor consisting of the leaser emitter and the photodiodes measures the arms deformation. The deformation of the whole structure leads to an undesired error in the end-effector position control. Using this concept of measurement enables the compensation of this inaccuracy. The simulation model is used for the optimization of the additional measurement concept.

This paper sheds light on a fuzzy-genetic system applied to optimize cabled-truss structures. The optimization procedure combines ground structure approach, nonlinear finite element analysis, genetic algorithm, and fuzzy logic. The latter is used to include expertise in the evolutionary search to classify and filter individuals with low survival possibility sp. The classification is based on a scale that varies from 0% to 100%, and the filtering depends on a threshold value Spt defined by the user. Particularly, the individuals with sp ≤ Spt are not evaluated, thereby decreasing the total number of evaluations. Although this approach proved suitable to reduce computational cost, the effect of different Spt values on the system's performance was not yet investigated. In that light, this work aims to present a sensitivity analysis of the fuzzy-genetic optimization system to variations of Spt. For that, the system was applied to ground structures with 10 elements and Spt values ranging from 0% to 100%. The results were compared by means of the analysis of variance test in order to investigate the effects of Spt on the system's performance and to identify the optimum Spt, which was found to be of 60% for the studied case.

Hybrid system for sizing and topology optimisation of cable-truss structures.Nonlinear finite element analysis of cable elements.Hybridisation of fuzzy logic and genetic algorithm.Optimisation of prestressed structures.Computational cost reduction through fuzzy filtering. This paper demonstrates an application of a hybrid fuzzy-genetic system in the optimisation of lightweight cabled-truss structures. These structures are described as a system of cables and triangular bar formations jointed at their ends by hinged connections to form a rigid framework. The optimised lightweight structure is determined through a stochastic discrete topology and sizing optimisation procedure that uses ground structure approach, nonlinear finite element analysis, genetic algorithm, and fuzzy logic. The latter is used to include expertise into the evolutionary search with the aim of filtering individuals with low survival possibility, thereby decreasing the total number of evaluations. This is desired because cables, which are inherently nonlinear elements, demand the use of iterative procedures for computing the structural response. Such procedures are computationally costly since the stiffness matrix is evaluated in each iteration until the structure is in equilibrium. Initially, the proposed system is applied to truss benchmarks. Next, the use of cables is investigated and the system's performance is compared against genetic algorithms. The results indicate that the hybrid system considerably decreased the number of evaluations over genetic algorithms. Also, cabled-trusses showed a significant improvement in structural mass minimisation when compared with trusses.

Stiff terms in second order ordinary differential equations may cause large computation time due to high frequency oscillations. Quasistatic approximations eliminate these high frequency solution components in the dynamical simulation of multibody systems by neglecting inertia forces. In the present paper, we study the approximation error of this approach using classical results from singular perturbation theory. The transformation of the linearly implicit second order model equations from multibody dynamics to the canonical (semi-)explicit form of first order singularly perturbed ordinary differential equations is studied in detail. Numerical tests for the model of a walking mobile robot with stiff contact forces between legs and ground show that the computation time may be reduced by a factor up to 10 using the proposed quasistatic approximation.

The paper deals with the new approach of the kinematical synthesis based on the reformulation of the synthesis computations as a time evolution of the nonlinear dynamical dissipative system. The synthesis/optimization objective functions are constructed based on the network of mechanism positions within the desired workspace. All synthesized parameters of the mechanism are in the associated dynamical system introduced as time-varying and generally different in the different positions. The important points and/or important lines are equipped with the fictitious masses and/or moments of inertia, the differences of parameters generates the correction forces, and the gradual dissipation of the kinetic energy is ensured by dampers connected between the inertial frame and the masses (sky-hook concept). The correction forces couple the auxiliary dynamical subsystems created in different positions. The nonzero correction forces are generated as long as the values of the corresponding parameters across the positions differ. The synthesis process is realized as the time evolution of such a system. The main advantage of the method for solving mechanisms’ synthesis is that it uses the unassembled configurations of the mechanisms by evolution of the time varying parameters. The mechanism search thus smoothly goes through the space of system parameters without inefficient penalization of the unassembled configurations. This space provides possible valuable solution of the more robust kinematical synthesis of the mechanisms. The applications for the different types of synthesis tasks and optimization of different objective functions like the optimization of the mechanism transmission or the multi-objective optimization of dexterity measure and the built-up space are straightforward, as described within the presented examples. The efficiency of the method can be improved using several re-activations of the evolution process.

This paper deals with the solution of three key problems for enabling the consideration of the massive parallelization for multibody dynamics. Instead of classical joints, the flexible joints with appropriate stiffness and damping are introduced in the multibody system, which enables to derive completely decoupled equations of motion and as a consequence to simulate them using massive parallel computing. Such formulation causes the uprise of high frequencies in the solution. Therefore, the heterogeneous multiscale method is used for numerical integration. However, three key problems had to be solved prior to such multibody simulation could be considered for further development. The problems are: the clear distinction of macro-model and micro-model in order to really reduce the eigenvalues of the integrated model, the completely decoupled procedure for estimation of reaction forces for each micro-integration restart, and the suitable choice of microintegration time length.

The paper deals with the research of the influence of design parameters on calibration of the machines. The calibrability is introduced as a mechanism property describing the sensitivity of calibrating dimension accuracy and end-effector positioning accuracy with respect to the accuracy of sensor measurements. The calibrability should be optimized in a very early stage of the design process. The optimization of calibrability leads to the minimization of the error transfer from sensors to end-effector and consequently to the improvement of the final accuracy of the machine operations. The calibrability should be used within the design process of a new parallel kinematical structures as a pendant of other traditional design criterions. The context of the new design criterion is discussed using the examples of parallel machines Trijoint 900H and Sliding Star. Finally the calibrability is used as a main design criterion of a spatial redundant parallel calibrating and measuring machine RedCaM.

Vehicle ride control depends not only on vehicle design, but also on the condition of the vehicle components, and on suspension components in particular. Moreover, vehicles currently in use are equipped with many kinds of electronic devices that assist drivers in their daily and emergency situations. These devices focus on active safety, which increases vehicle-handling capabilities, e.g. by a targeted intervention of the brakes on the individual wheels. These systems require correctly functioning wheel suspension, which is not guaranteed by used vehicles, as worn dampers have fewer damping capabilities and worn bushings result in improper wheel alignment. This paper presents a simulation study of the influence of worn suspension components such as dampers and bushings on the braking capabilities of vehicles. The stopping distance of vehicles as well as lateral shift is compared for different levels of worn and defective suspension components.

The paper deals with the optimization of the experimental functional model of the fibre driven tilting mechanism with three degrees of freedom and four drives. Measured orientation of the platform is realized by means of incremental sensors in central joint. The optimization of the calibrability and the sensor placement shows, that the measurement of the platform position (orientation in the spherical case) is necessary both for the good calibrability and for its accurate position control.

Design involves the formulation of a solution, such as a product specification, from initial requirements. Design in industrial and other contexts often involves the building and use of models that allow the designer to test hypotheses and learn from possible design decisions prior to building the physical product. The building and testing of models is a design process in its own right. Previous work in knowledge management, design rationale and the psychology of design has demonstrated that designers often vary from prescriptive methodologies of the design process and have problems appropriately describing their design activity in order to support design collaboration and the reuse of design artefacts. Drawing on this work, we support design collaboration and reuse structured according to key transformational episodes in the design process and the design artefacts they produce. To support this, we characterise the design task as progressing through a series of worlds, each comprising its own concepts and vocabulary, and supported by its own design tools. The design process can then be described in terms of important transformations that are made from one world to the next. This allows a targeted approach to rationale capture integrated with work practice and associated with products of the design process. This approach has been successfully deployed and tested in two industrial engineering companies. Findings included improved collaboration in design teams, effective reuse and improved training for new members of the design team. This work has more general implications for the development of design rationale methods and tools to support the design process.

The paper describes the extension of the composite rigid body formalism for the flexible multibody systems. The extension has been done in such a way that all advantages of the formalism with respect to the coordinates of large motion of rigid bodies are extended to the flexible degrees of freedom, e.g. the same recursive treatment of both coordinates and no appearance of O(n 3 ) computational complexity terms due to the flexibility. This extension has been derived for both open loop and closed loop systems of flexible bodies. The comparison of the computational complexity of this formalism with other known ap- proaches has shown that the described formalism of composite rigid body and the residual algorithm based on it are more efficient formalisms for small number of bodies in the chains and deformation modes than the usual recursive formalism of articulated body inertia.

The paper describes the multibody formalism based on natural coordinates and modified state space that is suitable for real-time applications. The complex multibody systems include closed loops and thus result into DAE equations. Their simulation then usually requires iterative stabilization. The described multibody formalism has two important properties making it suitable for real-time applications. Firstly, it provides the stable solution of DAE equations for multibody systems with kinematical loops without necessity of iterations. Secondly, it consists of system matrices with simple expressions (constant, linear or quadratic terms) for their elements and thus it is very suitable for massive parallelization. The resulting computational complexity is growing only linearly with the number of DOFs despite any occurrence of kinematical loops and it is about 5 times smaller than the recursive multibody formalisms.

Regular back door actuators in vehicles are currently quite fragile devices. Cruel handling by drivers causes frequent damage of both electronic and mechanical parts. The movement of the actuator is also associated with the possibility of injury. The paper presents use of mechatronic and inventive design methods for development of novel robust solution, which however still fits into current vehicle design and ensures safe operation.

The research field of the snake robots provides a large scale of new information. The snake robots locomotion in pipes represents one of many complicated problems attracting the attention only in recent time period. During this study an experimental environment was designed corresponding to the pipe of U shaped cross section. This article describes a new innovative kinematic structure enabling both rotary and translational movements of links of a snake robot. Combination of these two robot constrains in constructions provides new possibilities of locomotion in a confined space. The main work contribution consists in the analysis of geometric configuration of links in static fixation according to their displacements and required actuators electric power. In the experiment with physical model the method of digital image correlation was used because of the possibilities to take the movement of high dynamic range. Contribution of this experiment furnishes new information and new approach in solving the existing problem.

The article investigates the potential of controlled vehicle suspension for off-road vehicles. The primary question is whether the controlled vehicle suspension can reduce the deformation of the deformable off-road (soil) and can become a soil-friendly suspension. The article represents the preliminary study of this problem, in the sense that the realistic but simple models for the vehicle, the tyre—off-road contact, and the suspension control have been chosen. The results described demonstrate that the specific soil-friendly vehicle suspension exists and the off-road (soil) deformation can be significantly reduced. If an off-road vehicle with a passive (but optimized) suspension is repeatedly passed across an off-road with an initial bump, then the initial bump is increased and developed into a long wavy road after the bump. Such wavy roads are typically seen on the off-roads after passing many vehicles. If the same experiment is realized with an off-road vehicle with a controlled (semi-active or limited...

The paper deals with the design and control of an example of redundantly actuated parallel kinematic structure that can be a machine tool. The principle of redundant actuation brings parallel kinematic structures which do not have singular positions in workspace and which has increased dynamic, stiffness and accuracy properties. There is proposed a parallel kinematic structure called Sliding Star that has promising dynamic and stiffness properties. The conceptual design-by-optimization of this structure is briefly described. The redundantly actuated parallel kinematics have control problem due to mutual fighting of redundant drives. There is described the solution of this problem. Based on the investigated redundantly actuated parallel kinematics there has been built a laboratory prototype. The experimental results from the control of this prototype are briefly presented.

The majority of engineering designs can be described as configuration design. The solution of configuration design is not only the satisfaction of constraints and requirements, but the solution requires the optimized variant. However, there are usually multiple objectives and corresponding design problem in a multiobjective one. Even for relatively small problems the solution space is large and the computational complexity can be very high with exponential growth. Another problem of configuration design is the usual nonlinear and non-monotonic character of engineering design. The efficient computation of multiobjective global optimisation is a powerful general way for solving the nonlinearity and non-monotonicity of design problems.

In this paper, state-derivative and especially output-derivative feedbacks for linear time-invariant systems are derived using control approach similar to linear quadratic regulator (LQR). The optimal feedback gain matrices are derived for the desired performance. This problem is always solvable for any controllable system if the open-loop system matrix is nonsingular. Explicit expression of the state-derivative gain matrix is derived. Finally, simulation results are included to show the effectiveness of the proposed approach.

A procedure for solving the pole-placement problem for a linear single-input/single-output (SISO) systems by state-derivative feedback is described. This pole-placement problem is always solvable for controllable systems if all eigenvalues of the original system are nonzero. Then any arbitrary closed-loop poles can be placed to achieve the desired system performance. The solution procedure results in a formula similar to the Ackermann one. Its derivation is based on the transformation of a linear SISO system into Frobenius canonical form by co-ordinate transformation, then solving the pole-placement problem by state-derivative feedback and transforming the solution into the original co-ordinates. The solution is also extended to time-varying systems.