Добірка наукової літератури з теми "Pneumatic unit dynamics"

Robots that enable safe human-robot collaboration can be realized by using compliant drive units. In previous works, different mechanical designs of compliant pneumatic rotary drive units with similar characteristics have been presented. In this paper, we present the overall control approach that we use to operate one of these compliant pneumatic rotary drive units. We explain the mechanical design and derive the differential equation that describes the dynamics of the system. In order to successfully operate a pneumatic drive unit with three or more working chambers, the torque specified by the controller has to be split up onto the working chambers. We transfer the well-known field-oriented control approach from electric motors to the investigated pneumatic drive unit to create such a torque mapping. Moreover, we develop optimized torque mappings that are tailored to work with this type of drive unit. Furthermore, we introduce and compare two control algorithms based on different implementations of state feedback to realize position control. Finally, we present the step responses that we achieve when we implement either one of the control algorithms in combination with the different torque mappings.

The analysis of a thermo-pneumatic actuation unit for its use in a micropump has been carried out. Coupled thermo-mechanical simulations by finite element method (FEM) (with ANSYS software) were required because of the complexity of the device. The simulation results were validated by thermal and mechanical experimental results, showing a good agreement. FEM results have been used to extract a high level model of the actuation unit that can be used to estimate the maximum performance of the micropump operation with this actuation unit. In order to identify the best frequency of operation for the pump, a quality parameter has been defined based on the thermal dynamics of the actuation unit.

Introduction. Ratios for calculating the laden skip acceleration and speed at the motion start are required to calculate skip pneumatic winding plant cycle components. The ratios are the solution to the skip dynamics equation which takes into account the relationship between the flow generated by a power unit and air pressure. Research methodology. The dynamics equation including the dependence of the pressure on the flow rate (aerodynamic characteristic) in a general form is compiled. In a special case of the unit’s physical model, a discharge unit with a linear aerodynamic characteristic is used. Research result. For a particular case, equations are obtained that allow to theoretically describe the kinematic parameters of a skip in the period of unsteady motion. It is established that the skip acceleration, velocity and displacement are asymptotic functions. The obtained expressions for kinematic parameters make it possible to theoretically determine the duration of the acceleration period and the path that the ISSN 0536-1028 «Известия вузов. Горный журнал», № 1, 2021 121 skip takes during this period. A method for calculating skip dynamics during acceleration is proposed, which contains approximating formula conclusion for the power unit aerodynamic characteristics, its substitution into the dynamics equation, and obtaining skip kinematic parameters by solving the dynamics equation. Conclusion. The obtained relations allow to calculate skip dynamics during acceleration taking into account power unit aerodynamic characteristics, which is necessary to determine the working cycle time of the pneumatic winding plant.

In this paper an implementation of an adaptive control law for a pneumatic actuator is presented. Pneumatic actuators are of particular interest for robotic applications because of their large force output per unit weight, and their low cost. Stabilization of a pneumatic actuator is difficult if a high bandwidth closed-loop system is desired. This is because of the compressibility of air, and of the nonlinear characteristics of air flowing through a variable area orifice. Further complications arise from the geometry of the mechanism because the equations of motion are highly nonlinear. The order of the dominant dynamics is shown to vary with the position of the mechanicsm.

The pneumatic muscle is a pneumatic motor of the single-acting reciprocating motion. It is designed to create apullingforce. Return of the pneumatic muscle to its original position is provided by elastic deformation of its shell. A cylindrical membrane with the hard bottom and the lid provides the basis of the pneumatic muscle.The membrane cord is formed in the process of helically shaped CU-braid of the threads made from the super-hard synthetic fibres (for example, Kevlar). After the cord is filled with an elastomer, a strong, deformable and elastic shell is formed. An excessive pressure applied to the internal cavity of the membrane arises an extension of the tangent diagonal and a simultaneous shortening of the axial diagonal in the diamond-shaped cell, which is formed as a result of braid of cord threads. This results in pneumatic muscle’s retraction up to 25% of its original length, while creating a sufficiently large contraction force, which depends significantly on the contraction value.Using the cord structure of the MAS series pneumatic muscles of the company “FESTO” as an example, we have investigated a diamond-shaped cell deformation of the membrane and have defined a numerical dependence of its internal diameter and the volume of the internal cavity of the pneumatic muscle on the contraction value. This allowed us to develop a mathematical model of an idealized cylindrical membrane whose dynamics does not take into account a deformation force of the elastomer, filling a diamond-shaped cell.The experimental studies of industrial samples of the MAS 10 family of pneumatic muscles, carried out using a specially designed unit, allowed us to obtain their force characteristics. In the numerical representation, these characteristics turned out to be 2.5 ... 3 times less than the force characteristics of the pneumatic muscle with an idealized membrane, thereby allowing us to draw conclusions that the elastomer deformation forces have a significant influence. There is a proposal to take into account the elastomer deformation effect on the force characteristics of the pneumatic muscle by dint of the correction factor available from a comparative estimate of the force characteristics of the idealized membrane and the normalized force characteristics of the pneumatic muscles of the MAS family.The results of the performed studies allow us to predict the force characteristics of pneumatic muscles at the stage of their design and in-service.

The final stage of the cultivation of crops is harvesting. The quality of the operation depends on the annual result of the effectiveness of all previous work. It is important not only to harvest well, but to preserve the fertility of the soil and avoid soil compaction. The problem of compression is becoming more acute due to the massive use of heavy wheeled tractors and combines. The degree of soil compaction depends on the type of propulsion unit, the weight of the tractor and the number of passes of the units across the field. The negative impact of undercarriage systems on the soil should be considered when creating new machines based on new layout schemes, to reduce the structural weight, taking into account the dynamics and distribution of the center of mass of the variation in hook load. To reduce pressure and evenly distribute it is possible through the creation of more advanced propulsion and suspension systems. The purpose of this article is to analyze the most promising designs of the mobile agricultural machinery undercarriage systems, which can reduce the specific pressure on the ground, improve the throughput of agricultural machinery and provide a more comfortable planting and harvesting. At the moment, the following main directions of development of agricultural machinery undercarriage systems can be distinguished: pneumatic tracks, twin wheels, half-track, installation of rubber-reinforced tracks (RRT) and torsion as an elastic suspension element. The tests carried out confirmed that the installation of a changeable tracked propulsion unit can reduce the degree of soil compaction by 17-46 %, and the use of twin wheels showed an increase in pulling force by 20 % and a decrease in gauge depth by 40 %. The use of pneumatic trackers allows to increase the permeability of the transport vehicle on soils with a weak bearing capacity and at the same time minimize the damage that it can cause to the supporting base. Recently it is popular to operate the agricultural machinery, which uses rubber-reinforced caterpillar. Its caterpillar operational cycle if higher of 4-5 times comparing to those from metal. In addition, it allows to reduce vibration load and do the work at wet soil conditions. RRT is put both in the all-track version, and in the form of a wheel-caterpillar. This propulsion unit has a triangular shape of rubber tracks is mounted instead of wheels. Currently, individual torsion hangers of track rollers are widely used on tracked tractors. The advantages of the new torsion-balance suspension made it possible to increase the reliability and durability of tracked tractors undercarriage systems.

This paper studies the design of pneumatic soft-bodied bionic basic execution unit with soft-rigid combination, which can be used as an actuator for pneumatic soft-bodied robots and soft-bodied manipulators. This study is inspired by structural characteristics and motion mechanism of biological muscles, combined with the nonlinear hyperelasticity of silica gel and the insertion of thin leaf spring structure in the nonretractable layer. Response surface analysis and numerical simulation algorithm are used to determine the optimal combination of structural dimension parameters by taking the maximum output bending angle of the basic executing unit as the optimization objective. Based on Odgen’s third-order constitutive model, the deformation analysis model of the basic execution unit is established. The physical model of pneumatic soft-bodied bionic basic execution unit is prepared through 3D printing, shape deposition, soft lithography, and other processing methods. Finally, the motion and dynamic characteristics of the physical model are tested through experiments and result analysis, thus obtaining curves and empirical formulas describing the motion and dynamic characteristics of the basic execution unit. The relevant errors are compared with the deformation analysis model of the execution unit to verify the feasibility and effectiveness of the design of the pneumatic soft-bodied bionic basic execution unit. The above research methods, research process, and results can provide a reference for the research and implementation of pneumatic and hydraulic driven soft-bodied robots and grasping actuators of soft-bodied manipulators.

The paper presents a model of a pneumatic piston unit and analyzes dynamic processes taking place in the unit generating periodic signals. Nonlinearities and feedback occurring in flow and vibration processes are determined. A method of nonlinearity and feedback compensation by input parameters of air streams is presented. [S0022-0434(00)00201-X]

This paper reports on the control structure of the pneumatic biped "Lucy." The robot is actuated with pleated pneumatic artificial muscles which have interesting characteristics that can be exploited for legged machines. They have a high power-to-weight ratio, an adaptable compliance and they can reduce impact effects. The current control architecture focuses on the trajectory generator and the tracking controller, which is divided into a computed torque controller, a delta-p unit, a PI position controller and a pressure bang-bang controller. The trajectory generator provides polynomial joint trajectories while the computed torque, combined with the delta-p unit, calculates the required muscle pressure levels. The PI and bang-bang controller work at a pressure level to cope with modeling errors and to set the pressures in each muscle. The control design is divided into single support and double support, where specifically the computed torque differs for these two phases. The proposed control architecture is evaluated with a full hybrid dynamic simulation model of the biped. This simulator combines the dynamical behavior of the robot with the thermodynamical effects that take place in the muscle-valves system. The observed hardware limitations of the real robot and expected model errors are taken into account in order to give a realistic qualitative evaluation of the control performance and to test the robustness. A preliminary implementation of the presented controller on the real biped, representing a walking motion of the robot while both feet are in the air, is discussed. This first implementation shows already promising results concerning tracking performance of the proposed control architecture. It confirms that the pneumatic tracking system can be used for a dynamic application such as a biped walking robot.

Original designs of pneumatic-tyre movers and vehicle suspension are proposed. Their use will permit to increase reliability, operation durability, ride comfort, and cross-country capability of machine and tractor unit; to improve operator work conditions; to decrease vertical vibration and dynamic loads on supporting surface as well as soil compaction.