Approximate Straight-line Mechanism Research Articles

基于MATLAB的近似直线机构的解析分析与实现

基于MATLAB的近似直线机构的解析分析与实现

Design of compliant straight-line mechanisms using flexural joints

Straight-line compliant mechanisms are important building blocks to design a linear-motion stage, which is very useful in precision applications. However, only a few configurations of straight-line compliant mechanisms are applicable. To construct more kinds of them, an approach to design large-displacement straight-line flexural mechanisms with rotational flexural joints is proposed, which is based on a viewpoint that the straight-line motion is regarded as a compromise of rigid and compliant parasitic motion of a rotational flexural joint. An analytical design method based on the Taylor series expansion is proposed to quickly obtain an approximate solution. To illustrate and verify the proposed method, two kinds of flexural joints, cross-axis hinge and leaf-type isosceles-trapezoidal flexural(LITF) pivot are used to reconstruct straight-line flexural mechanisms. Their performances are obtained by analytic and FEA method respectively. The comparisons of the results show the accuracy of the approach. Both examples show that the proposed approach can convert a large-deflection flexural joint into approximate straight-line mechanism with a high linearity that is higher than 5 000 within 5 mm displacement. This can lead to a new way to design, analyze or optimize straight-line flexure mechanisms.

1P1-A18 GAを用いた近似直線運動機構の設計

1P1-A18 GAを用いた近似直線運動機構の設計

The inverted slider-crank used for the design of an approximate straight-line mechanism

The inverted slider-crank used for the design of an approximate straight-line mechanism

協調制御を必要としない歩行機械に関する研究

Legged locomotion over irregular terrain is composed of body propelling motion and terrain adapting motion. Although conventional walking machines with three active degrees of freedom (d.o.f) for each leg can adapt their feet on irregular ground using flexible leg freedom, such machines generally require a tremendously complex control scheme for the body propelling motion, because cooperational control of leg freedoms in stance is required for a system with several closed kinematic chains between the body and the ground. To cope with this problem, a walking machine with decoupled freedoms, described in this paper, is based on the idea that body propelling motion is realized by only one degree of freedom and can be perfectly decoupled from the freedoms for terrain adaptability. In this type walking machine, the control system is perfectly released from the control of closed kinematic chains. Therefore it can be expected that the control algorithm will become much easier than that of conventional walking machines having three active d.o.f. per each leg. First, the authors discuss such walking machines and make clear the quadruped walking model with minimum active d.o.f. through basic considerations of freedoms of walking machines. Next, according to observations of animal locomotion, a hexapod walking machine (MELWALK) with decoupled freedoms using an approximate straight line mechanism is developed in order to realize faster and simpler walking machines than the quadruped one. As the foot pattern of this walking machine is limited to only one pattern, other kinds of freedoms are established to implement a body direction changing motion and a terrain adapting motion. Rotational freedom other than propulsion is added to implement the body direction changing motion, and extension and contraction freedom to the legs are also added to implement the terrain adapting motion. Although more than two active d.o.f. for each leg are desirable for terrain adaptability, the proposed walking machine has only one active d.o.f. for simplicity. Experiments are carried out to certify the body propelling motion, terrain adapting motion and body direction changing motion. It can be recognized from the trajectory of LED that the body proceeds along an approximate straight line close to an exact one. Body direction changing motion is implemented with relatively high speed. Furthermore in order to check energetic efficiency, the power consumed by DC motor is also measured using MELWALK MARK-I. Several features of the proposed hexapod walking machine are revealed through these experiments.

A hexapod walking machine with decoupled freedoms

Legged locomotion over irregular terrain is composed of body-propelling motion and terrain-adapting motion. Although conventional walking machines with three degrees-of-freedom for each leg can adapt their feet on irregular ground using flexible leg freedom, such machines generally require a tremendously complex control scheme for the body-propelling motion. A walking machine with decoupled freedoms is based on the idea that body-propelling motion is realized by only one degree-of-freedom, and this freedom can be perfectly decoupled from the freedoms for terrain adaptability. As an application of such a walking machine, a hexapod walking machine using an approximate straight line mechanism was developed and several basic experiments were performed to demonstrate the properties of this type of walking machine.

擬似直線機構を利用した6足歩行機械に関する基礎的研究

Although legged locomotion machines equipped with three active degrees of freedom per each leg possess great flexibility on irregular terrain, such machines need very complicated software in controlling and coordinating leg motion. As a result, such machines perform awkwardly except a particular legged machine even when they walk on a flat plane and although they have flexible mechanism, multi-functioned walkings are not realized under the existing circumstances.Under these circumstances, the authors propose such a fixed gait type legged machine (MELWALK MARK-III) as can attain two dimensional walking and terrain adaptability. In this particular model, the fixed gait (alternating tripod gait) is realized by only one active degrees of freedom using an approximate straight-line mechanism and seven other active degrees of freedom are added for two dimensional walking and terrain adaptability. Mechanism and basic control system on the proposed legged machine are described precisely with the comparison of conventional machines equipped with three active degrees of freedom per each leg.Experiments are carried out to certify the basic movements and the simplicity of control algorithm. In order to check the dynamic effectiveness, the specific resistance and the payload limit are also measured. Several features of the proposed legged machine are revealed through these experiments.

On the synthesis of certain straight-line mechanisms

A direct method is presented for the synthesis of a large class of approximate straight line mechanisms based on a set of two equations describing the center of curvature of the path (the coupler curve) of an arbitrary point on the coupler of a crank-slider mechanism with an off-set. Several examples are discussed to establish the capability of the proposed set of equations to incorporate the classical approximate straight-line mechanisms (e.g. Watt, Chebyshev and Scott-Russell) as the special cases of the synthesis which can be constructed directly based on graphical considerations. A straightforward design of a luffing-crane mechanism and a graphical construction of a special mechanism which generates two mutually orthogonal straight lines are also presented to further illustrate the general versatility of the proposed method of synthesis.