Balanced Manipulator Research Articles

Синтез и исследование адаптивной системы управления силовыми взаимодействиями в упругих механизмах многозвенных манипуляторов

Предложена методика синтеза адаптивной электромеханической силокомпенсирующей системы управления шарнирно-балансированным манипулятором с многозвенной структурой упругого исполнительного механизма. Приведено математическое описание электромеханической системы с трёхмассовой механической частью. Получены аналитические выражения для определения параметров адаптивного управляющего устройства при изменении массы перемещаемого объекта и жесткости механических передач и звеньев. Проведено исследование механической части манипулятора без электропривода и с применением предложенной адаптивной системы управления усилиями в упругом исполнительном механизме с синтезированным корректирующим устройством при изменении положения и массы перемещаемого груза от 20 до 160 кг.

Mathematical description of elastic mechanisms of force compensating manipulator

Improvement of control systems for manipulators and robots was required implementation complex automation of production processes. It is necessary to have a reliable mathematical description of elastic mechanisms interacting during operation to solve problems of analysis and synthesis of control devices of force compensating manipulators. The work goal is the development of the mathematical description of elastic executive mechanisms of the ShBM-150M balanced manipulator. Studies have shown that low-frequency components of moved weight elastic vibrations are due to flexural deformation of a manipulator’s shoulder and arm. Inertia equivalent values of manipulator links are changed by 2.2 and 37 times during manipulator operation with a constant load value. Total flexural deformation of shoulder and arm deflection is 25 mm during changing mass per 100 kg. And parameters of the mathematical model can be changed by 11 times, which needs adaptive control use.

Determination of Effective Damping of Elastic Mechanism Vibrations of Balanced Manipulator by Electric Drive

Research results of electric drive using capability determination are presented for vibrations damping of elastic mechanisms of ShBM-150M type manipulator. Symbolic expressions are listed for calculation of rational speed controller’s parameters in electric drive coordinates subordinate regulation system providing minimal vibration amplitude of torque in elastic transmission and executive mechanism speed. Comparison of effective damping of manipulator lift elastic vibrations was completed tuning motor speed controller with standard recommendation about infinite stiffness transmissions and rational controller’s parameters

Goals and Problems of Improving of Electromechanical Control System of SHBM-150M Type Balanced Manipulator

The movement of different objects in area is main part of most operations. Often that movements are performed by various types of balanced manipulators. The analysis of a Russian manipulator of ShBM-150M type was completed, the specifics design and applied sensorless vector control system of induction motor are considered. The disadvantageous of manipulator work due to the current control system are detected. The factors of low position precision of cargo at fixation on tags are determined. The elastic vibrations of the manipulator mechanical part, which adversely affect for its work quality, have been experimentally identified and researched. The design model of multi-mass mechanical system is presented. The improvement goals of the control system of ShBM-150M manipulator are defined for upgrade of technical parameters, ease of operation and functional capability.

Разработка и промышленное внедрение электромеханических силокомпенсирующих систем управления усилиями в исполнительных механизмах шарнирно-балансирных манипуляторов

Разработка и промышленное внедрение электромеханических силокомпенсирующих систем управления усилиями в исполнительных механизмах шарнирно-балансирных манипуляторов

Determination of Maximum Damping Efficiency based on Electric Drive Vibrations of Elastic Mechanisms

The main factors that determine maximum values of elastic mechanical vibrations of operating machines with an electric drive were detected. The efficiency of different ways of vibrations passive damping of elastic mechanisms was reviewed. The conditions were determined and recommendations about the choice of parameters of electric drives ensuring minimum dynamic efforts in springy elements of mechanical gears were given. It was found that damping of vibrations in the elastic mechanisms caused by changing of disturbing effort by the electric drive is the most effective if the resonant frequency of mechanical vibrations is in the range of frequencies of electric drive dropping. The estimation of marginal efficiency by the electric drive of vibrations in elastic mechanical gears has been performed, the areas of reasonable application of damping devices and the electric drive for the reduction of dynamic efforts in springy elements of mechanical gears were defined. The practical implementation of the proposed recommendations has been carried out for the MP100 type balanced manipulator.

Многофакторный выбор электромеханического модуля для перспективного сбалансированного манипулятора

The method of efficient multifactorial determination of transmission gear parameters for selection of an electric motor of the vertical load motion system equipped with a prospective balanced manipulator was applied. The complex approach to selection of the power circuit for the balanced manipulator is based on considering three main restrictions: synchronization of electric motor and manipulator actuator rates, drive operation with the lowest possible value of the maximum torque and providing a stand-by mode of alive electric motor at the rated load. The required value of the gear reduction radius should be selected from the allowable range with the method of a compromise rational value of the reduction radius that could comply with all considered conditions. Rational parameters of the electromechanical module were selected at varying value of the motor reduction radius with due regard to the minimization criterion of the total maximum motor torque. Thus, the compromise selection of the required parameters of the electromechanical module was provided. It is recommended to apply high-speed synchronous electric motors with permanent magnetic field for development of prospective balanced manipulator.

Design and experimental evaluation of a dynamically balanced redundant planar 4-RRR parallel manipulator

Shaking forces and shaking moments in high-speed parallel manipulators are a significant cause of base vibrations. These vibrations can be eliminated by designing the manipulator to be shaking-force balanced and shaking-moment balanced. In this article an approach for the design and evaluation of high-speed dynamically balanced parallel manipulators is presented and applied to a comparative experimental investigation of a balanced and unbalanced DUAL-V planar 4-RRR parallel manipulator. For precise simulation of the manipulator motion, the inverse dynamic model of the manipulator is derived and validated. Experiments show that the balanced manipulator has up to 97% lower shaking forces and up to a 96% lower shaking moment. For small inaccuracies of the counter-masses or for a small unbalanced payload on the platform, base vibrations may be considerable for high-speed manipulation, however their values remain significantly low as compared to the unbalanced manipulator. For the balanced manipulator the actuator torques are about 1.6 times higher and the bearing forces are about 71% lower as compared to the unbalanced manipulator.

Dynamic Characteristics of Balanced Robotic Manipulators with Joint Flexibility

SUMMARYThe mass balancing of robotic manipulators has been shown to have favorable effects on the dynamic characteristics. In actual practice, however, since conventional manipulators have flexibility at their joints, the improved dynamic properties obtainable for rigid manipulators may be influenced by those joint flexibilities. This paper investigates the effects of the joint flexibility on the dynamic properties and the controlled performance of a balanced robotic manipulator. The natural frequency distribution and damping characteristics were investigated through frequency response analyses. To evaluate the dynamic performance a series of simulation studies of the open loop dynamics were made for various trajectories, operating velocities, and joint stiffnesses. These simulations were also carried out for the balanced manipulator with a PD controller built-in inside motor control loop. The results show that, at low speed, the joint flexibility nearly does not influence the performance of the balanced manipulator, but at high speed it tends to render the balanced manipulator susceptible to vibratory motion and yields large joint deformation error.

Dynamic characteristics of balanced robotic manipulators with joints flexibility

SummaryThe mass balancing of robotic manipulators has been shown to have favorable effects on their dynamic characteristics. In actual practice, however, since conventional manipulators have flexibility at their joints, the improved dynamic properties obtainable for rigid manipulators may be influenced by those joints flexibilities. This paper investigates the effects of the joints flexibility on the dynamic properties and the controlled performance of a balanced robotic manipulator. The natural frequency distribution and damping characteristics were investigated through frequency response analyses. To evaluate the dynamic performance a series of simulation studies of the open-loop dynamics were made for various trajectories, operating velocities, and joint stiffnesses. These simulations were also carried out for the balanced manipulator with a PD controller situated inside the motor control loop. The results show that, at low speed, the joints flexibility does but little influence the performance of the balanced manipulator, but at high speed it tends to render the balanced manipulator susceptible to vibratory motion and yields large joints deformation errors.

An approach to point-to-point control for direct-drive SCARA-type robots.

In recent years, attention has been paid to direct-drive for industrial robots which are essential to factory automation. Direct-drive robots, which are directly actuated with no gear reducer, have no backlash, low friction and good mechanical stiffness. This results in the excellent repeatability of positioning, that is, an order of magnitude better than that of gear-drive robots. It is, however, more prominent in the design of control system for direct-drive robots that the arm inertia variation depending on the arm configuration and the Coriolis and centrifugal torques are directly reflected to the motor axes due to the direct coupling.In this paper, a direct-drive robot with a two degree-of-freedom is developed for planer assembly tasks. The motion of the manipulator arm is constrained within a horizontal plane, so that this type of robot is referred to as a SCARA (Selective Compliance Assembly Robot Arm)-type robot. A balanced manipulator arm, the purpose of which is to cancel the inertia variation and nonlinear effects, is introduced to the direct-drive robot, thus leading to improved control performance as well as simple manipulator dynamics.In addition, the combination of feedforward compensation and a new approach to positioning control is proposed to perform stable and fast positioning without overshooting.

Design of a compact statically balanced direct-drive manipulator

SUMMARYThis paper addresses the conceptual design of direct-drive manipulators which have good promise for high speed, high precision manipulation. In the design methodology presented, the procedure begins by considering the kinematic aspects and ends by configuring manipulator structures with promising kinematic and dynamic characteristics. Based on the conceptual design considerations, a novel 3 DOF (RRR) direct-drive manipulator is proposed and analyzed. The manipulator structure has only five links and a compact configuration. Manipulator kinematics and dynamics are analyzed. Design guidelines are derived for static balancing of the manipulator and for minimizing the inertias driven by the motors. Operational configurations that either improve or worsen the kinematic and dynamic behaviour or characteristics of the manipulator are identified. The proposed design has an advantage over many currently known direct-drive manipulators for achieving two desirable mechanical features, namely: static balancing and compactness (smaller driven inertias).

On the Dynamics and Control of Robotic Manipulators with an Automatic Balancing Mechanism

Non-linear characteristics and uncertainty in manipulator dynamics caused by payload effects are major hurdles in controller design. To overcome such hurdles the authors have introduced an automatic balancing concept which has been proved to reduce the non-linear complexity in manipulator dynamics as well as to remove gravity loading. This paper examines the characteristic features of balanced manipulator dynamics in more detail and presents an efficient control algorithm suitable for the dynamics. Since the dynamics of a balanced manipulator are characterized by partially configuration-independent inertial properties, the present algorithm adopts two different control concepts ‘the computed torque control’ for the joint having coupled, configuration-dependent inertia and ‘an optimal constant feedback control’ for the joints having configuration-independent inertia. To evaluate the proposed control algorithm, simulation studies were made over a wide range of manipulator speeds and payloads. Based upon the simulation results, the efficiency of the controller is discussed in detail.