Just L. Herder

Non-invasive control interfaces for intention detection in active movement-assistive devices

AbstractActive movement-assistive devices aim to increase the quality of life for patients with neuromusculoskeletal disorders. This technology requires interaction between the user and the device through a control interface that detects the user’s movement intention. Researchers have explored a wide variety of invasive and non-invasive control interfaces. To summarize the wide spectrum of strategies, this paper presents a comprehensive review focused on non-invasive control interfaces used to operate active movement-assistive devices. A novel systematic classification method is proposed to categorize the control interfaces based on: (I) the source of the physiological signal, (II) the physiological phenomena responsible for generating the signal, and (III) the sensors used to measure the physiological signal. The proposed classification method can successfully categorize all the existing control interfaces providing a comprehensive overview of the state of the art. Each sensing modality is briefly described in the body of the paper following the same structure used in the classification method. Furthermore, we discuss several design considerations, challenges, and future directions of non-invasive control interfaces for active movement-assistive devices.

Development of a statically balanced arm support: ARMON

People with neuromuscular diseases can benefit from devices that assist their motoric capabilities. Different categories can be distinguished for different patient groups, ranging from robotic manipulators to non-powered orthoses. Robotic manipulators can be used by people with virtually no muscle force, whereas non-powered orthoses require at least acceleration and deceleration effort. This paper proposes a hybrid solution, constituting a non-powered orthosis that can be electronically adjusted to varying load. An overview of prototype development would be presented, including the design of linkage, balancer, interface and appearance. A preliminary evaluation with users is also provided.

Stable Precision Grasps by Underactuated Grippers

The ability of underactuated hands to grasp small objects is very limited, because the precision grasp is normally unstable. The goal of this paper is to achieve stable precision grasps by means of simple design modifications of the distal phalanges of the fingers. These modifications comprise the curving of the contact area of the distal phalanx, the application of a mechanical limit to prevent hyperextension of the distal phalanx, and the application of a compliant joint between the proximal and distal phalanges. A model is developed to calculate the limits of the finger dimensions in order to achieve stable precision grasps for different object sizes. An experimental setup is used to test the grasp stability and to verify the calculated results. It is concluded that stable precision grasps exist for the combination of concavely curved distal phalanges with a mechanical limit or with a compliant joint, if the limits to the finger dimensions are satisfied.

Evaluation of new user interface features for the MANUS robot arm

New user interface features and a new user interface for the MANUS robot arm, were designed in order to reduce the high cognitive and physical load that users experience when controlling the MANUS. These interface features, and the new interface, were evaluated for their performance. The following results were obtained. A new method of switching between control modes proved to be a significant improvement. However, the introduction of a new control mode, called pilot control mode, increased the cognitive and physical load of the MANUS users. The users were content with the new interface and with the extra functionalities that were added in this interface, such as the collaborative controller, with which some degrees of freedom of the MANUS can be controlled automatically, and with an alternative centre of rotation of the gripper that allows for new movements of the gripper.

A Compliant Rolling Contact Joint and Its Application in a 3-DOF Planar Parallel Mechanism With Kinematic Analysis

This paper first presents the concept and the fabrication of a new type of compliant rolling joint which combines the advantages of compliant mechanisms with those of rolling link mechanisms. In this joint, flexible bands create the necessary constraints to enforce a rolling movement between two links. Then, the rapid prototyping techniques used for the compliant rolling joint fabrication are described. The kinematics of one application of this joint in a 3-DOF planar parallel mechanism are then presented. A semigraphical method was used to find the solutions to the inverse kinematic problem. Finally, the workspace analysis and the velocity equations are presented.Copyright

Mechanical manipulator for intuitive control of endoscopic instruments with seven degrees of freedom

Performing complex tasks such as vascular anastomosis in minimally invasive surgery (MIS) is demanding due to a disturbed hand-eye co-ordination, the application of non-ergonomic instruments with limited number of degrees of freedom (DOFs) and a lack of three-dimensional perception. Robotic tele-manipulatory systems enhance surgical dexterity by providing up to seven DOFs. They allow the surgeon to operate in an ergonomically favourable position with more intuitive manipulation of the instruments. Robotic systems, however, are very bulky, expensive and do not provide any force feedback from the tissue. The aim of our study is to develop a simple mechanical manipulator for MIS. The Minimally Invasive Manipulator (MIM) is a purely mechanical device. When manipulating the handle of the MIM, the surgeons wrist and grasping movements, which are essential for suturing, are directly transmitted to the deflectable instrument tip in seven DOFs. It gives the surgeon direct control of the instrument tip. First phantom experience indicates that the system functions properly. The MIM provides force feedback to improve safety. A set of MIMs seems to be an economical and compact alternative to robotic systems and will offer more surgeons the capability to perform complex MIS and to shorten their learning curve.

Feasibility Study of a Fully Compliant Statically Balanced Laparoscopic Grasper

Compliant mechanisms have many advantages over their rigid-body counterparts. One disadvantage however is the fact that motion of the mechanism is associated with elastic energy storage in the compliant parts. This is a problem especially in cases where accurate force transmission is of primary concern, such as in medical graspers. A solution to this problem is to statically balance the elastic forces by the addition of a spring force compensation mechanism, such that the effect of the compliance is neutralized. The complete resulting mechanisms resulting from this concept are called statically balanced compliant mechanisms (SBCMs). This paper presents a feasibility study into the design of a grasper for medical purposes and demonstrates that the concept is possible and practically viable. It is shown that the compliant gripper of a laparoscopic forceps can be statically balanced with a single-piece compliant compensation mechanism, with a balancing error of only 0.03N while dimensions are such that the compensation part of the mechanism can be stored inside the hand grip of the instrument.Copyright

Statically Balanced Compliant Micro Mechanisms (SB-MEMS): Concepts and Simulation

Compliant mechanisms play an important role in micro mechanical structures for MEMS applications. However, the positive stiffness of these mechanisms remains a significant drawback. This stiffness can be compensated by including a static balancing mechanism (SBM), resulting in a statically balanced compliant micro mechanism (SB-CMM). This paper presents concepts and simulation results of such mechanisms, which could be applied to MEMS (SB-MEMS). Two categories of SB-CMMs are presented for different situations: the balancing force and travel path are either (1) perpendicular to each other, or (2) parallel to each other. The presented concepts provide compliant mechanisms with a finite zero stiffness range at the start or at a further predefined position of the overall mechanism travel range, respectively. The simulation results confirm the validity and performance of the presented concepts, which have been optimized for further evaluation. Incorporation of these concepts can ultimately result in a reliable, smaller, and energy efficient microsystem, having a larger useful travel range.Copyright

Design of a Statically Balanced Tensegrity Mechanism

The combination of static balancing and tensegrity structures has resulted in a new class of mechanisms: Statically Balanced Tensegrity Mechanisms. These are prestressed structures that are in equilibrium in a wide range of positions, and thus exhibit mechanism-like properties. This paper describes the design of a prototype model of a statically balanced tensegrity mechanism based on a classic tensegrity structure.Copyright

Behavior of arthroscopic irrigation systems

In the literature, no consensus exists about optimal irrigation of joints during arthroscopic operations. The goal of this paper is to study the behavior of irrigation systems resulting in the proposal of guidelines for optimal irrigation. To this end, optimal irrigation is defined as the steady state of irrigation of a joint in which a sufficient positive intra-articular pressure and a sufficient flow are maintained. A model of the complete irrigation system was created to schematically elucidate the behavior of pump systems. Additionally, clinical experiments were performed during arthroscopic knee operations in which the pressure at different locations and the irrigation flow were measured. The combination of model prediction and clinical results could well be used to derive guidelines, since the clinical results, which showed considerable variation, were used to verify the model, and the model could be used to explain the typical trends. The main findings are twofold the set pressure is always higher than the intra-articular pressure, and the scope–sheath combination has a significant influence on irrigation control, because of its large restriction. Based on the results, we advice to increase the set pressure during active suction, and to include the sheath–scope combination in the control loop.