Passive Mechanical Components Research Articles

Generic evaluation of operating experience with regard to the ageing behaviour of passive mechanical components in nuclear power plants

Abstract Since the mid-90s, GRS has been dealing systematically with the assessment of the influences of ageing on the safety of nuclear power plants. This also involves the generic evaluation of operating experience. In the following, the procedure, methodological approaches and relevant results are presented in an exemplary manner for passive mechanical components. The results show that the number of events influenced by ageing phenomena that have so far occurred in German plants is low and that measures were taken where necessary to detect, monitor and control any changes due to ageing. As new insights may emerge over time concerning the assessment of the ageing behaviour of the components, it is considered necessary to continue with the ongoing generic evaluation of operating experience in order to obtain timely indications of any safety-relevant changes.

The structure of a sliding sensory system for a self-adaptive prehensor

The quality of the prehension is determined by the mobility state of the prehension object.The emphasis on sliding within the self-adaptive prehensor, proposed in the paper, is achieved by correlating the parameters generated by the rotation sensor (encoder), the contact sensor and the angular position of the stepper motor.The rotation of the encoder is influenced by the active and passive mechanical components in the prehensor jaws.In this way, it is obtained a 2D sliding sensory system. The sensory system is a complex mechatronic system that can adapt to most industrial robots of different sizes and types, including the cartesian type. The prehension of the objects is accomplished through a sensory technique which integrates all software and hardware operations to achieve the image of the two directions grip. The sensory system has a resistive position sensor in its structure which determines the angular position of the axis of rotation of the execution element. The inductive position sensor is the second sensor of the system. It highlights the mechanical tensionless contact on the prehensile object. The sliding of the object is emphasized by a resistive position sensor. An important role in programming the prehensor is the correlation between the software information from the three sensing elements with the stepper motor that achieves the force required for the prehension.

ハードウェアベース安全装置を搭載した足関節用アシストスーツの開発 (品質機能展開を用いた設計)

When developing rehabilitation assist suits, safety consideration for patients is one of the most important issues. In this paper, we propose an ankle joint assist suit with a velocity-based safety device and a commercial torque limiter. The velocity-based safety device switches off the assist suit’s motor if it detects an unexpected high joint angular velocity. The torque limiter cuts off the torque transmission if it detects an unexpected high joint torque. These devices work even when the assist suit’s computer breaks down, because they consist of only passive mechanical components without actuators, controllers, or batteries. First, we describe the design requirements for this assist suit. Next, we clarify the relationship between the design requirements and the assist suit parts by using Kato’s multispace-quality function deployment (M-QFD). Finally, we present the assist suit design incorporating this relationship.

A process chain for integrating piezoelectric transducers into aluminum die castings to generate smart lightweight structures

The application of piezoelectric transducers to structural body parts of machines or vehicles enables the combination of passive mechanical components with sensor and actuator functions in one single structure. According to Herold et al. [1] and Staeves [2] this approach indicates significant potential regarding smart lightweight construction. To obtain the highest yield, the piezoelectric transducers need to be integrated into the flux of forces (load path) of load bearing structures. Application in a downstream process reduces yield and process efficiency during manufacturing and operation, due to the necessity of a subsequent process step of sensor/actuator application. The die casting process offers the possibility for integration of piezoelectric transducers into metal structures. Aluminum castings are particularly favorable due to their high quality and feasibility for high unit production at low cost (Brunhuber [3], Nogowizin [4]). Such molded aluminum parts with integrated piezoelectric transducers enable functions like active vibration damping, structural health monitoring or energy harvesting resulting in significant possibilities of weight reduction, which is an increasingly important driving force of automotive and aerospace industry (Klein [5], Siebenpfeiffer [6]) due to increasingly stringent environmental protection laws. In the scope of those developments, this paper focuses on the entire process chain enabling the generation of lightweight metal structures with sensor and actuator function, starting from the manufacturing of piezoelectric modules over electrical and mechanical bonding to the integration of such modules into aluminum (Al) matrices by die casting. To achieve this challenging goal, piezoceramic sensors/actuator modules, so-called LTCC/PZT modules (LPM) were developed, since ceramic based piezoelectric modules are more likely to withstand the thermal stress of about 700°C introduced by the casting process (Flössel et al., [7]). The modules are made of low temperature cofired ceramic (LTCC) tapes with an embedded lead zirconate titanate (PZT) plate and are manufactured in multilayer technique. For joining conducting copper (Cu) wires with the electrode structure of the LPM, a novel laser drop on demand wire bonding method (LDB) is applied, which is based on the melting of a spherical CuSn12 braze preform with a liquidus temperature Tliquid of 989.9°C (Deutsches Kupfer-Institut Düsseldorf, [8]) providing sufficient thermal stability for a subsequent casting process.

メカニカル安全装置を搭載したロボットスーツの開発

We have proposed a robot suit with two hardware-based safety devices - the “velocity-based safety device” and the “torque-based safety device”. The robot suit assists a patient's knee joint. The torque-based safety device stops the robot suit if it detects an unexpected high joint torque. Similarly, the velocity-based safety device stops the robot suit if it detects an unexpected high joint angular velocity. The safety devices work even when the computer breaks down, because they consist of only passive mechanical components without actuators, controllers, or batteries. In this paper, we analyze the transient responses of the velocity-based safety device to some ramp inputs. Furthermore, we verify the effectiveness of the velocity-based safety device on the basis of the analysis result.

S1110104 メカニカル安全装置を搭載したロボットスーツの開発 : 安全装置の有効性の検討([S111-01]第20回卒業研究コンテスト(1),機素潤滑設計部門)

Safety is one of the most important issues in rehabilitation robot suits. We have developed a rehabilitation robot suit with two mechanical safety devices. The robot suit assists a patient's knee joint. We call one of the safety devices the "velocity-based safety device" and the other the "torque-based safety device". The velocity-based safety device switches off the motor if it detects an unexpected joint angular velocity. Similarly, the torque-based safety device switches off the motor if it detects an unexpected joint torque. The safety devices can work even when the computer breaks down, because they consist of only passive mechanical components without actuators, controllers or batteries. In this paper, we review the characteristics of the safety devices and the rehabilitation robot suit equipped with the safety devices. Furthermore, we present experimental results to verify the effectiveness of the safety devices in the robot suit having a weight simulating a patient's leg.

Buffet suppression in long-span suspension bridges

We study the aerodynamic control of long-span suspension bridges and seek to raise the critical flutter wind speeds, while simultaneously suppressing buffeting. The control system design study is based on a simple flexible bridge section model that interacts with a constant-velocity air stream. A streamlined bridge deck is assumed and non-steady thin aerofoil theory is used to describe the interactions between the bridge deck and the air stream. Classical turbulence models, first developed in the aircraft industry, are used to model the buffet forces acting on the deck. While a wide variety of control systems is possible, we focus on a compensation scheme that can be implemented using passive mechanical components such as springs, dampers and a rack and pinion mechanism. A single-loop control system is investigated that controls a trailing-edge flap by sensing movements of the bridge deck; several such mechanisms are contemplated. The first finding is that the critical wind speed for flutter can be greatly increased, with good robustness characteristics, through passive feedback control. It is also possible simultaneously to suppress flutter using the same passive mechanical controller by solving a passive mixed H 2 / H ∞ control problem. The effect of flexible controller mounting arrangements are considered briefly.

Aeroelastic Control of Long-Span Suspension Bridges

The modeling, control, and dynamic stabilization of long-span suspension bridges are considered. By employing leading- and trailing-edge flaps in combination, we show that the critical wind speeds for flutter and torsional divergence can be increased significantly. The relatively less well known aerodynamic properties of leading-edge flaps will be studied in detail prior to their utilization in aeroelastic stability and control system design studies. The optimal approximation of the classical Theodorsen circulation function will be studied as part of the bridge section model building exercise. While a wide variety of control systems is possible, we focus on compensation schemes that can be implemented using passive mechanical components such as springs, dampers, gearboxes, and levers. A single-loop control system that controls the leading- and trailing-edge flaps by sensing the main deck pitch angle is investigated. The key finding is that the critical wind speeds for flutter and torsional divergence of the sectional model of the bridge can be greatly increased, with good robustness characteristics, through passive feedback control. Static winglets are shown to be relatively ineffective.

Chapter 12 - Hair Cell Mechanotransduction: The Dynamic Interplay Between Structure and Function

Hair cells are capable of detecting mechanical vibrations of molecular dimensions at frequencies in the 10s to 100s of kHz. This remarkable feat is accomplished by the interplay of mechanically gated ion channels located near the top of a complex and dynamic sensory hair bundle. The hair bundle is composed of a series of actin-filled stereocilia that has both active and passive mechanical components as well as a highly active turnover process, whereby the components of the hair bundle are rapidly and continually recycled. Hair bundle mechanical properties have significant impact on the gating of the mechanically activated channels, and delineating between attributes intrinsic to the ion channel and those imposed by the channel's microenvironment is often difficult. This chapter describes what is known and accepted regarding hair-cell mechanotransduction and what remains to be explored, particularly, in relation to the interplay between hair bundle properties and mechanotransducer channel response. The interplay between hair bundle dynamics and mechanotransduction are discussed.

Control of smart exercise machines. I. Problem formulation and nonadaptive control

Concerns the design of intelligent controllers for a class of exercise machines. The control objective is to cause the user to exercise in a manner which optimizes a criterion related to the user's mechanical power. The optimal exercise strategy is determined by a biomechanical behavior of the individual user, which is assumed to satisfy an affine force-velocity relationship dependent on the body geometric configuration. Consequently, the control scheme must simultaneously: 1) identify the user's biomechanical behavior; 2) optimize the controller; and 3) stabilize the system to the estimated optimal states. Moreover, to ensure that the exercise machine is safe to operate, the control system guarantees that the interaction between the exercise machine and the user is passive. We formulate the control problem and propose a controller structure which satisfies the safety requirement and is capable of causing the user to execute an arbitrary exercise strategy if the user's biomechanical behavior is known. The controller is of the form of a dynamic damper and can be implemented using only passive mechanical components.

Contraction of flap muscle in the cardioarterial valve of Panulirus japonicus

1. 1. The posterior cardioarterial valve of Panulirus japonicus consists of two crescent flaps. 2. 2. Free edges of the flaps are concaved by contraction of the cardiac muscle. Thus, the valve is opened widely during systole. 3. 3. The valve closes with straightening of the free edges whenever the flap muscle is contracted by the pericardial hormone, proetolin. 4. 4. When the valve is stretched by the pericardial septum, active tension produced by the flap muscle is doubled, whereas passive tension becomes ten times as high as the active tension. 5. 5. The active and passive mechanical components of the flap appear to be connected in parallel.