To reduce the surgical trauma to the patient, minimally invasive surgery is gaining considerable importance since the eighties. More recently, robot assisted minimally invasive surgery was introduced to enhance the surgeon's performance in these procedures. This resulted in an intensive research on the design, fabrication and control of surgical robots over the last decades. A new development in the field of surgical tool manipulators is presented in this article: a flexible manipulator with distributed degrees of freedom powered by microhydraulic actuators. The tool consists of successive flexible segments, each with two bending degrees of freedom. To actuate these compliant segments, dedicated fluidic actuators are incorporated, together with compact hydraulic valves which control the actuator motion. Especially the development of microvalves for this application was challenging, and are the main focus of this paper. The valves distribute the hydraulic power from one common high pressure supply to a series of artificial muscle actuators. Tests show that the angular stroke of the each segment of this medical instrument is 90°.

Integrated high pressure microhydraulic actuation and control for surgical instruments.

This paper proposed a nonlinear mathematical model for a 4-port pneumatic nozzle-flapper type servo valve with dual fixed orifices and dual nozzles. In this model, the influence of the flow force was also included. The determination of the flow force on the flapper was proposed using an experimental approach. The effectiveness of the proposed model was verified by comparing experimental and simulated results. This comparison confirmed the influence of flow force on the static and dynamic behavior of the servo valve. A linear model, which was derived from the nonlinear model, showed an applicable range of about ±30% of rated input current. A practical, order-reduced linear model, which neglects the dynamics of the torque motor and the armature-flapper, was also proposed. The order-reduced model was suitable for systems with large load volumes.

https://journals.riverpublishers.com/index.php/IJFP/article/download/566/313

Modelling of a Nozzle-Flapper Type Pneumatic Servo Valve Including the Influence of Flow Force

Since the emergence of digital hydraulic technology, it has achieved good results in intelligence, integration, energy saving, etc. After decades of development, and it has also attracted wide attention in the industry. However, for many years, the definition of digital hydraulic technology has differed between researchers, and there is no uniform definition. Such a situation affects the development of it to a certain extent. Therefore, this paper gives the exact definition of digital hydraulic technology based on a large number of researches on it. At the same time, the paper analyzes the research status and developmental process of the such a technology, and we forecast the development trend of it.

Review and Development Trend of Digital Hydraulic Technology

Our development program fabricated a proportional control valve that exclusively uses water as its working fluid. The valve is equipped with a spool, and the spool is directly driven by a proportional solenoid that is modified for water use. Characteristics of the proportional solenoid are described first in this report while proving its performances similar to those of the conventional oil hydraulics.Following, structural characteristics of the water hydraulic proportional control valve are discussed. Water, the valve's working fluid, is low in lubricity and viscosity; therefore, hydrostatic bearings that support the spool are installed in the valve. In addition, to stabilize movement of the spool, damping orifices are provided. Particularly, the hydrostatic bearing portion is designed such that it minimizes the total leakage including bearing flow while obtaining load carrying capacity. The constant flow from the hydrostatic bearings prevents water from decaying in the valve. Lastly, the paper introduces experimental results of cylinder positioning controlled by the developed water hydraulic proportional control valve to verify its satisfactory performances as a control valve.

Development of water hydraulic proportional control valve

To address the environmental problems and the safety of hydraulic systems, the development of novel water hydraulic systems using working fluids such as tap water are being developed successfully. In this study, we aim to develop a proportional water hydraulic valve using a proportional poppet as the main valve, which has an on—off function as well as a proportional function. The proposed proportional poppet-type water hydraulic valve has a simple structure with a control orifice that passes to the pilot orifice at both sides of the conventional poppet. Experiments verified that the relation between the main flowrate and pilot flowrate of the developed valve is linear and that the dynamic characteristics of the proportional poppet are satisfactory. Also, the developed valve was verified to be suitable for pulse width modulation (PWM) control and practical use for the control of water hydraulic systems.

Development of a proportional poppet-type water hydraulic valve

An electrohydraulic servovalve that uses fresh water as a pressure medium (water hydraulic servovalve) is developed. conventional electrohydraulic servovalve cannot be operated with such a hostile fluid. In this paper, we explain the structure and functions of components, and the relationship between them, as well as the developmental procedure of the water hydraulic servovalve. The basic idea for the servovalve is to support the spool of the valve with hydrostatic bearings and to lead the water from the bearings to the flapper-nozzle system. The hydrostatic bearings constitute a laminar restriction that takes the place of the turbulent restriction in the conventional flapper-nozzle system. We also explain the design procedure of the hydrostatic bearing in the valve and the relationship between electromagnetic elements and fluidic elements. The water hydraulic servovalves fabricated show good characteristics of smooth motion, endurance and controllability, as well as good dynamic characteristics.

Yuhichi Usami

Papers

Development of a Water Hydraulic Servovalve.

Development of a Water Hydraulic Servovalve

Mmp3 in synovial fluid tends to upregulate prior to cartilage degeneration with mice oa model.

The effect of different timing of mechanical stress to the healing tendon after achilles tendon rupture in mice

Suggestion of new ptoa mice model induced by mechanical stress without surgery