Zbyněk Šika

Extended Ground-Hook - New Concept of Semi-Active Control of Truck's Suspension

SUMMARY This paper deals with the novel control concept, so called ground-hook for active and mainly semi-active suspension of vehicles with the ultimate objective to minimize the tyre-road forces and thus the road damage. The basic ground-hook concept is extended to the several variants which enable to decrease criteria of road damage as well as to increase drivers comfort for a broad range of road unevennesses. Parameters of control law are determined by the parameter optimization for generally nonlinear model. The influence and interaction of the damping rate limits and time constants of variable shock absorbers are also taken into account. The influence of implementation of more complicated truck models is also discussed.

Development of Semi-Active-Road-Friendly Truck Suspensions

Abstract Within the EC project Copernicus SADTS (Semi-Active Damping of Truck Suspensions and its Influence on Driver and Road Loads) a semi-active suspension for SKODA-LIAZ truck prototype is being developed. The objective is to decrease the dynamic road-tyre forces in order to reduce the road damage. It was necessary to find a suitable truck prototype, develop and verify a simulation model, propose different control concepts, and implement them on the truck prototype. This paper briefly describes the development stages of the project and the results finally achieved.

DYNAMIC MODEL OF TRUCK FOR SUSPENSION CONTROL

Abstract This paper presents the modelling of heavy duty vehicle prototype for a semi-active suspension design. Two basic models have been developed - the model of a passive vehicle and the model of a vehicle equipped with controllable shock absorbers. The models serve for evaluation of several proposed control schemes. The identification and verification experiments, which has been provided on the truck are described as well as the software tools used in the process of simulation.

Evaluation of Dynamic Capabilities of Machines and Robots

The paper deals with the formulation and thesolution of the global dynamic problem for multibody systemsgenerally described by redundant coordinates (DAE equations) andwith a redundant number of actuators.Within the dynamics of multibody systems two basic well-known problems have been investigated: the solution of direct dynamicsand the solution of inverse dynamics. Both of these problems enableus to solve in each time instant the relation between the motiondescribed by positions, velocities, accelerations and the actingforces. However, such solutions obtained in isolated timeinstants do not provide us with the global overview about thedynamic capabilities of a mechanical system, i.e. about theaccessible motion described by accessible positions, accessiblevelocities, accessible accelerations and the required (given)forces. Thus, besides the two basic dynamical problems there isa third one: the global dynamic problem.The formulation of the global dynamic problem, the generalmethods for its solution and the specific methods for itssolution for robots and manipulators are included.

An investigation of properties of the forward displacement analysis of the generalized Stewart platform by means of general optimization methods

The method for the determination of all solutions of the forward displacement analysis of the generalized Stewart platform is proposed and described. The kinematic problem is transformed to the problem of global minimization of the specially created objective function. The problem is formulated in the domain of complex numbers, the general optimization methods are used for the solution. The presented method is very easily applicable on the manipulators of arbitrary structure, it has practically unlimited potential of parallelization.

Soil-friendly off-road suspension

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-active) suspension, then the initial bump is decreased, and the development of the wavy road is suppressed. The usage of soil-friendly off-road suspension can be for both agricultural and military vehicles.

Development of Semi-Active Truck Suspension

Abstract Within the EC project Copernicus SADTS (Semi-Active Damping of Truck’s Suspension and Its Influence on Driver and Road Loads) the semi-active suspension for Liaz truck prototype is being developed. The objective is to decrease the dynamic road-tyre forces in order to reduce the road damage. It was necessary to develop a suitable truck prototype, its simulation model, different control concepts and to implement the semi-active suspension. The paper describes the development stages and the so far achieved results. The full mathematical model was the basis for simplified models for control designs and served as a reference model for comparison of different control concepts. The spatial three dimensional simulation model has been developed and verified. The base model includes also the reference inputs of excitation and the different criteria for performance evaluation. The purpose of the model was to investigate the vertical dynamics though with the influence of antisymmetry of uneveness and lateral motion. A number of different control concepts have been considered. Possible suitable control concepts have been selected from existing classical as well as advanced control design methods. Also several within this project newly developed approaches have been added. There have been considered the control concepts of simple approaches (sky hook), classical approaches (LQR), multi-objective multi-parameter optimization (ΜΟΡΟ), fuzzy and neural networks, robust control design. The newly developed control concepts are ground-hook and combination sky/ground-hook, robust multi-objective optimization based on Taguchi approach, fuzzy control based on optimization, structural approach (separate control of frame and cabine suspension). The performance criteria for evaluation have been road forces, driver’s seat and load accelerations, robustness against change of parameters. The comparison has been done on the simulation model in SIMPACK program package connected with MAT-LAB/SIMULINK. Very promising results have been achieved up to now by combination of sky-ground hook and by the classical LQR control. The evaluation of other concepts is still in progress. Hardware and field tests are scheduled for 1997.

Design of Redundant Parallel Robots by Multidisciplinary Virtual Modelling

The paper deals with the description of design methodology for redundant parallel robots based on multidisciplinary virtual modelling. The redundant parallel robots means redundantly actuated parallel robots. The parallel robots have many advantages as low moving masses, higher stiffness of truss structure, all drives on the frame, but they suffer from many problems like appearance of singularities and thus smaller workspace, collisions of links. These drawbacks of parallel structures can be removed by the principle of redundant actuation [4, 1]. This means that the platform is supported and driven by more bars with drives than the necessary number of degrees of freedom (DOF). This principle not only deletes the singularities from workspace as more combinations of links in number of DOF are not simultaneously in singular positions, but it brings further advantages, especially increased and more uniform dynamic capabilities, stiffness, accuracy.

Dynamic Model of Aircraft Passenger Seats for Vibration Comfort Evaluation and Control

The paper deals with the development of the seat dynamical model for vibration comfort evaluation and control. The aircraft seats have been tested extensively by vibrations on the 6 DOF vibrating platform. The importance of the careful comfort control together with the flight mechanics control is namely stressed for the blended wing body (BWB) aircrafts. They have a very large fuselage, where the mechanical properties (accelerations, angular accelerations) vary considerably for different seat places. The model have been improved by adding of dynamical models of the aircraft passenger seats identified by the measurements on the 6 DOF vibrating platform. The experiments, their results and the identification of the dynamical seat model are described. The model is further modified by adding of the comfort evaluation norms represented by dynamical filters. The structure and identification of the seat model is briefly described and discussed.

KNOWLEDGE SUPPORT FOR VIRTUAL MODELLING AND SIMULATION

The paper describes an approach to providing knowledge support for virtual modelling and simulation (VMS). The design methodology, based on multidisciplinary virtual modelling and subsequent simulation, is essential for contemporary engineering design [1], but specifically for the design of complex mechatronic machines [3]. Additionally, current engineering design is multidisciplinary and therefore based on team work. The teams are often geographically distributed and would benefit from greater support for collaboration. Engineering design also draws heavily on previous experience and therefore it is essentially to build and maintain comprehensible and re-usable archives of previous cases. This is also true of simulation models.