Ball Screw Mechanism Research Articles

Mechatronics and control of a long-range nanometer positioning servomechanism

Since the manufacturing accuracy of semiconductor and biochemical products is increased to nanometer level gradually, the development of long-range positioning servomechanism has become a hot research topic. The piezoelectric actuator is widely chosen to design precise positioning system for achieving the sub-micro or nano-position. However, their motion range is only 100 μm. Here, a long-range nanometer positioning servo system with AC servo motor and ball screw mechanism is built for the precision manufacturing purpose. It needs a special design control algorithm to obtain quick transient response and precise steady state accuracy. A new model-free fuzzy controller is designed to control this low-cost motion stage for achieving nanometer step response positioning. It has a novel gain auto-tuning strategy in response to the transient or steady state responses requirement. The experimental results show that this approach can reach more than 30 cm stroke and the step response error is less than 60 nm.

A practical control method for precision motion—Improvement of NCTF control method for continuous motion control

The present paper describes a practical control method for a precision motion system and the performance thereof. For practical use, high motion control performance and ease of design and controller adjustment are desired. A nominal characteristic trajectory following control (NCTF control) has been investigated to realize high performance and ease of application of point-to-point (PTP) positioning. The controller comprising a nominal characteristic trajectory (NCT) and a PI compensator is free from exact modeling and parameter identification. In the present paper, the NCTF control is modified in order to improve the control performance of continuous motions such as tracking and contouring motions. The NCTF controller for continuous motion (referred to as Continuous Motion NCTF controller) has a structure that is almost identical to the conventional NCTF controller and is designed using the same design procedure. The Continuous Motion NCTF controller is applied to ball screw mechanisms, and its motion control performance is evaluated from the experimental tracking, contouring, and positioning control results. The experimental results prove that the Continuous Motion NCTF controller achieves the same positioning performance as the conventional NCTF controller, and generally achieves better continuous motion control performances than PI-D or conventional NCTF controllers. In 0.25 Hz and 100-nm radius circular motion, the experimental tracking errors for Continuous Motion NCTF were smaller than 10 nm.

A novel robust disturbance compensation scheme for d.c. servomotors

A novel friction and modelling uncertainty compensation scheme for a ball-screw table system is presented, consisting of an inverse of the nominal model with an input deduction, a filter, and an integral term. This control scheme can compensate for frictional effects and modelling uncertainty inherent in the ball-screw mechanism. In addition, when further combined with a conventional sliding-mode controller (SMC), this controller can help to counteract the effects of residual frictional torque and residual modelling uncertainty. The proposed control scheme successfully compensates for frictional effects and modelling uncertainty without requiring any prior knowledge of the friction model. Simulation and experimental results confirm the ability of the proposed scheme to compensate for the effects of friction and modelling uncertainty in a practical application.

Practical control method for ultra-precision positioning using a ballscrew mechanism

Abstract This paper describes a practical control method for nanometer level point-to-point positioning (PTP) using a conventional ballscrew mechanism. A nominal characteristic trajectory following controller (NCTF controller) is used for the ultra-precision positioning. The controller design, which is comprised of a nominal characteristic trajectory (NCT) and a PI compensator, is free from exact modeling and parameter identification. The NCT is determined from an open-loop experiment and the PI compensator is used to make the mechanism motion to follow the NCT. The compensator gain values are restricted by the practical stability limit of the control system, which is easy to determine. Using a high integral gain causes excessive overshoot, so an antiwindup integrator is used to improve the system performance. The NCTF control system achieves a positioning resolution of 5 nm and is robust against friction variations.

Positioning and tracking of a linear motion stage with friction compensation by fuzzy logic approach

In this paper, the development of a fuzzy controller that compensates for nonlinear friction in a linear motion stage is presented. The experimental work and instrumentation set up is presented for this research. Based upon a nonlinear friction model, friction parameters were estimated from experimental results. Simulation and experimental validation on a ball-screw mechanism is presented, showing the effectiveness of the proposed controller. Furthermore, it is shown that the proposed fuzzy control scheme offers several implementation advantages such as smaller control effort, and reduced effect of measurement noise. Moreover, the fuzzy logic methodology displays superior performance when compared to a conventional PID controller. It also shows good and robust tracking with respect to system parameters variation.

Study on Vibration Control Device Using Power Generator

In this paper, the authors developed a vibration control device (V.C.D.) using a power generator and a flywheel which is suitable for vibration suppression of a structure. The V.C.D. consists of a ball screw, a ball nut, a flywheel, a gear, and a power generator. The linear motion is converted into a rotating motion by the ball screw mechanism. The damping force is generated by the power generator, and controlled by an electric resistance at the terminal of the power generator. The inertial force is created by the flywheel which is attached to the end of the screw shaft. Since these forces are magnified by the ball screw and the gear, the V.C.D. has resisting force characteristics as the sum of the controllable damping force and the inertial force in the low frequency range. In order to investigate dynamic properties, a test V.C.D. is manufactured, and the resisting force characteristics are measured by using a vibration actuator. The experiments of frequency response are carried out using a shaking table, and the experimental results are compared with the theoretical results. The seismic responses are calculated under a semiactive control based on Linear Quadratic Regulator, and the effects of the vibration suppression of the V.C.D. are discussed experimentally and numerically.

Kinematic optimization of ball-screw transmission mechanisms

Abstract The paper proposes a method for the kinematic optimization of transmission mechanisms, where non-circular (NC) gears are used to perform a mechanical control on the output motion. The investigation presented here deals with the motion control of a ball-screw transmission mechanism. The objective is lowering the peak acceleration value of the screw, by designing a pair of variable radius gears as a driving mechanism. The kinematic characteristics of the ball-screw mechanism are analyzed by means of non-dimensional motion equations in order to formulate the optimization problem. A genetic algorithm (GA) is then implemented to optimize the objective function, and a penalty method is used to fulfil the design rules. The kinematic analysis of the optimal mechanism revealed a 37% reduction of the peak acceleration of the screw in comparison with a constant pitch screw, operated at a constant speed. A kinematic simulation is used to validate the method.

Measurements of Transient Driving Forces Generated by a Linear Motor and a Ball Screw Mechanism, and Comparisons to Those Static Characteristics

Transient driving forces generated by a linear motor and a ball screw mechanism including a rotational servomotor were measured and compared to those static characteristics. The static relationships between the motor currents and the output force (torque) were linear. In the linear motor drive system, the step response of the driving force was 1/10 slower than that of the motor current. In the rotational servomotor, the torque response was oscillatory with 800Hz frequency and 0.01 damping ratio. In the ball screw drive mechanism, the driving force response was deeply depended to the preload force and was 1/100 slower than that the motor current. It is noted that the ball screw mechanism generated the driving force after the servomotor rotated. These dynamics should be considered in a usual position control design.

1P1-B01 カウンタウェイトを利用したワイヤ懸垂型マニピュレータの位置決め制御

A wire suspended manipulator is proposed for extending its working space. A manipulator is fixed on a plate suspended by three wires, and a counter-weight driven by a ball screw mechanism is also introduced under the plate. In a wire suspended manipulator, a base may incline due to the motion of the manipulator. A method of eliminating the swinging motion of the base plate by feedback control of the counter-weight is proposed.

5133 新回転直動変換機構の理論検討(S63-7 トラクション・CVT,S63 伝動装置の基礎と応用)

We have originated a mechanism for converting rotary motion into linear motion for a linear actuator. This mechanism is composed of a columnar-shaped rod, a holder member supported around the rod that is rotatable relative to the rod, and rollers supported for rotation on the holder member. The rod is comprised of a thread having a predetermined lead angle. The axial angle of each of the rollers relative to the axis of the rod is set to be almost equal to the lead angle of the thread of the rod. Each of the rollers is comprised of annular grooves, which mesh with the thread of the rod. If the holder member is rotated, the rod will move linearly. As the result of a theoretical study on the mechanism, the efficiency of the mechanism is expected to be equal to that of the ball screw mechanism, and its thrust will be larger.

산업용 PCB 부품삽입 자동화 시스템 개발

A automatic component inserting system for industrial PCB is developed in this paper. This system has not been developed in Korea. Most domestic companies produce PCB manually. This process requires highly-skilled staff. Therefor, we developed a PCB inserting system for automation of the process and improved productivity. There are low parts in this system; press, table, tool change and control part. A hybrid press cylinder with pneumatic and hydraulic is used in the press part. The table part consists of pneumatic actuators, stepping motors and ball-screw mechanism. In the tool change part, upper tools can be exchanged automatically for the inserting of various components. The control part consists of motor drivers, PLCs and power supply.

Kinematic Analysis of the Ball Screw Mechanism Considering Variable Contact Angles and Elastic Deformations

The theoretical analyses developed by Lin et al. 6 for the kinematics of the ball screw mechanism have been partly adapted for the present study. In order to better understand the sliding behavior arising at two contact areas, the analyses of a ball bearing, while accounting for elastic deformation, are modified through coordinate transformations prior to their applications to the analyses for the ball screw mechanism. The influence of differing the parameters such as friction coefficient, normal force acting on the ball, and contact angle on a ball-screw’s mechanism at two contact areas are evaluated. The results of the ball-screw’s mechanical efficiency achieved by the present model are displayed to compare with those evaluated based on the model of Lin et al. Substantial differences exist in the results evaluated by these two models, especially those created at high screw rotational speeds.

Control of a Civil Structure Using an Electric Machine with Semiactive Capability

This paper concerns the implementation of a brushless DC machine as a force actuator, for use in suppressing vibrations in civil structures. The machine has the dual capability of operation as an active as well as semiactive device. It operates semiactively by using the machine as a generator to convert mechanical energy to electrical energy which is then dissipated. The electrical network uses electronic switching to control the power flow from the machine. With the machine shaft connected to a gear reducer and ballscrew mechanism, the result is a device that resembles a linear damper with a controllable damping coefficient. The only external electrical power required is that which is needed to support the control system intelligence and to control the transistors, enabling the device to be operated on battery power. As an example of an application of such an actuator, simulations are performed in which the semiactive device is used to control a three-story structural model, with acceleration feedback control. The structural control system design approach is the well-established “clipped-optimal” method. Results suggest that this actuator is effective in simultaneously suppressing the interstory drifts and the absolute accelerations of the structure. A comparison is made to a similar configuration using a magnetorheological damper as the semiactive force device.

2613 ボールねじの玉の運動挙動に及ぼす保持ピースの影響

Using a magnetized ball and hall elements arranged on the nut and the return tube, the authors measured the ball motion and the vibration of ball screw which incorporates resin retaining pieces between balls rotating at the shaft speed in the range of 120〜950rpm. The results were compared with not only the experimental results using the same type of normal ball screw but also the analytical results calculated based on the kinematic geometry of ball screw mechanisms. The ball motion in the ball screw became smooth by insertion of the retaining pieces and the vibration was fairly restrained. Especially, when the ball screw operated at a high speed, both the ball rotation and the ball circulation in the ball screw with retaining pieces were faster than those in the normal type without retaining pieces and the measured values well agreed with the analytical values.

2453 ボールねじの玉の運動挙動計測に関する研究

In order to make clear the high speed operating limit or the seizure resistance limit of the ball screw, it is necessary to grasp the actual ball motion in the ball screw, and the development of measuring method of the ball motion has been expected. In the present paper, using a magnetized ball and hall elements arranged on the nut and the return tube, the authors tried to measure the ball motion in the ball screw (ZFT4020) rotating at the shaft speed in the range of 120∿950rpm. The results were compared with the analytical results calculated based on the kinematic geometry of ball screw mechanisms. When the magnetic circuit attached to the measuring system, it became possible to observe the changes in the hall voltage, and the measured values such as the rotational speed of ball revolution and ball rotation almost agreed with the analytical values.

Mechanism Design of Wrist Joint for an Articulated Manipulator.

Motion transform mechanisms are designed for driving the wrist joint of a manipulator whose power sources(motors)are installed on the base in order to reduce masses and moments of inertia of arms. The wrist joint is composed of a spherical five-link mechanism of 2 DOF(degrees of freedom)and two linear-rotational motion transforms of Stephenson six-link mechanisms. Rotational motions of motors are transformed to linear motions by means of ball screw mechanisms, and then these motions become inputs of linear-rotational motion transformers which are driving the spherical five-link mechanism. Kinematic constants of the linear-rotational motion transformer are determined by means of a random search of the Stephenson six-link mechanism of its structural errors and forces acting on pairing elements. It is shown experimentally that the linear-rotational motion transformer is useful for the mechanism to drive the wrist joint.

Active Suspension of Truck Seat

The driver’s seat of a heavy duty truck is usually mounted on a spring–damper assembly anchored to the cab floor. To improve riding comfort, this study investigated the effects of mounting a computer‐controlled actuator in parallel with the traditional spring–damper assembly. A dynamic model of the seat is represented by a two degree‐of‐freedom system, including a cushion. In this paper, a control system is designed, using optimal control theory, which minimizes rms vertical acceleration at a point representing the driver’s hip point. In this system, accelerations of the hip point, the seat frame and the cab floor are picked up and integrated to obtain the state variables to be fed back and fed forward to the actuator through a digital computer. The actuator is constructed with electric servo‐motor and ball‐screw mechanism. The experimental study was carried out on a shaker, which simulates the vibrations of the cab floor in actual service. Results were obtained for both a dummy and a real human body. The vibration test produced rms accelerations of the seat and the hip point of about 1.0 m/s2 without the actuator, while the rms accelerations were suppressed to about 0.5 m/s2 at a rms input voltage to the servo‐motor of 1.0 V.

Contact Stress Analysis in Ball Screw Mechanism Using the Tubular Medial Axis Representation of Contacting Surfaces

A simple method is presented for analysis of contact stresses and deformation conditions between the bearing balls, screw, and nut of the ball screw mechanism. The method is based on representation of contact geometry and curvature analysis of contacting surfaces using a generalization of the medial axis transform (MAT) to tubular surfaces. Simplified Hertzian contact solutions are obtained using the curvature information. The results are approximate but do include the effect of complex thread profiles as a result of the helical grooves and are suitable for mechanical design purposes.

Active Suspension of Truck Seat.

The driver's seat of a heavy-duty truck is usually supported by a spring-damper assembly on the cab floor. This passive suspension isolates the driver from vibration of the cab floor effectively except for a 2 to 3 Hz vibration, which still leads to an uncomfortable ride for drivers ; thus it is desirable to achieve isolation from this low-frequency vibration. To improve riding comfort of the driver's seat, we propose a newly designed active suspension system, where an actuator is installed in parallel with the spring-damper assembly. The actuator is constructed using a DC servo-motor and ball-screw mechanism. A dynamic model of the seat is represented by a two-degree-of-freedom system including a cushion, but influences between foot and floor, arm and steering wheel etc. are neglected. The control system is designed using optimal control theory to minimize rms acceleration of a driver's hip point (seat cushion surface). In this system, accelerations of the hip point, the seat frame and the cab floor are measured and integrated to obtain the state variables to be fed back and fed forward. An experimental study was carried out on a shaker realizing vibration of the cab floor of the truck, and the active seat suspension system achieved satisfactory performance for the human body.

Kinematics of the Ball Screw Mechanism

This paper studies the kinematics of the Ball Screw Mechanism (BSM) with the aim of developing a foundation for understanding the motion of the balls and their contact patterns with the contacting elements. It is shown that there is always slip between the balls and the nut or screw, and therefore, the no-slip condition assumed in the BSM literature is not attainable. The effect of contact deformation on the motion of the balls is also studied and is used to develop the pattern of the constant sliding lines of contact between the ball and the screw or the nut. The results have applications in efficiency analysis, design, wear evaluation and finite element modeling of the BSM.