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In this paper, stepping over a zero height obstacle with minimal actuation is studied for a limit cycle walker modeled as a double inverted pendulum. The obstacle position is estimated by stereo vision. Actuation is realized by a constant torque per step on the hip and a push-off collinear to the trailing leg. Stepping over the obstacle must be accomplished with the obstacle position exactly on a predefined position in between the legs with the final state right after push-off being equal to the initial state. Thus, at least two steps must be taken to perform this task, such that the first step is used to make sure the relative position of the obstacle is correct. In the best case scenario, the obstacle is exactly in between the legs during a nominal walk. In that case, actuation does not have to be adjusted with respect to the nominal actuation. In the worst case scenario the obstacle is exactly at a stepping position. In that case, a translation of the step positions is needed. For stepping over in two steps this is not possible; this is only possible for a small range around the best case scenario. For stepping over in three steps this is possible when actuation is applied according to the optimization results presented.

Running robots often have their center of mass (CoM) located on the hip. This decouples the pitching and CoMdynamics and therefore allows for simple control schemes. However, by creating an offset between the CoM and the hip, and herewith introducing coupling between the pitching and CoMdynamics, the performance of the running robot might possibly increase. In this simulation study, we calculated the optimal CoMlocation for a running robot with hip actuation. We measured the performance of the system as the largest step-down and push that can be corrected in one or two steps. We found that the largest step-down can be corrected in one step when the CoM is located above the hip. The largest push on the other hand can be corrected when the CoM is located under the hip. For two-steps recovery strategies, placing the CoM exactly on the hip is the worst option out of all possible CoM-locations. In this case, the corresponding disturbance rejection is approximately a factor 10 worse than for the optimal CoM-location. Therefore, we conclude that placing the CoM of the torso on the hip is far from optimal.

The particular category of the underactuated grippers is chosen for the automation of the item picking in distribution centers. The underactuated grippers have fewer degrees of actuation than degrees of freedom, so they are mechanically simpler than the fully-actuated grippers, and they are able to adapt to objects regardless of their shapes. However, the existing underactuated grippers found in the literature are regarded overdesigned because more than enough passive elements are included. This paper is aimed to design and build a more simplified but still workable underactuated gripper for the item picking. The designed gripper contains a cable-pulley driven underactuated finger which has two phalanges, and an opposite fixed finger. Moreover, the fingertip of the underactuated finger is intended to move along the ground where the target object is laid. The dimensions of the gripper are selected in order to achieve the following two tasks: picking the cylindrical objects from the ground and retaining the grasp during a lifting transportation. The experiment setup fails to drive the fingertip of the underactuated finger moving along the ground, but it is shown that the designed gripper is still able to fulfill these two tasks, except for the case that when the initial spacing between the moving underactuated finger and the object is rather large.

The majority of existing problems within conventional prosthetic fingers are related to the use of conventional rigid links and kinematic joints and to the lack of adaptability of the finger. In this paper these problems are solved by the design of a fully compliant under-actuated prosthetic finger. At first a basic structure was defined. Subsequently a Pseudo Rigid Body method was used for a type synthesis and rough dimensional analysis in order to determine the topology of the conceptual design. In order to evaluate the grasping behavior of the conceptual design, four mock-ups were created. Detailed dimensioning design was performed by semi automatic numerical analysis using a finite element method in which the conceptual design was used as an initial input. A prototype based on this final design was manufactured and experimentally evaluated. It was found that utilizing the concepts of under actuation and compliance solved the identified problems within conventional prosthetic fingers. As a result of the design process and the use of a predefined structure a fully compliant underactuated finger with a monolithic structure and distributed compliance was obtained. In addition to the application field of prosthetics the design shows potential of being applied in the field of robotics and graspers.

The evaluation of steering systems can be enhanced by replacing the test driver by a driver model capable of mimicking the driver’s needs, wants and limitations. This model can subsequently be used to find the optimal steering system design by using computerized optimization routines, or by developing a steering system that adapts to the driver while driving. Also vehicle stability control systems (VSC) can be improved by driver centered design, providing artificial force cues via the steering wheel that aid in controlling the vehicle. A suitable driver model needs to incorporate a neuromuscular (NMS) structure. The validated model of de Vlugt (2004) is used as a basis. Since this model is identified for isometric conditions only, two main adaptations are needed before this model can be used for driver simulation during more extreme maneuvers. First, the driver’s reflexes are given a moving reference point determined by the desired steering wheel position. Second, the muscle forces needed to generate the desired steering wheel angle are calculated by a so called inverse internal model. This model reflects the driver’s learnt dynamics of his arms and the system to be controlled. The new driver model shows to be capable of steering large angles and simultaneously modeling the physical limitations of the driver. Optimization techniques were used to find the optimal driver model parameters, depending on his driving mood and driving task. The same optimization techniques were used to find the optimal steering ratio, where the optimal ratio showed to changes significantly depending on the mood and task. This indicates there is room for improving steering systems as they currently mainly depend on vehicle velocity.

In this paper we show a way to create stable full body motion for a humanoid robot without defining all joint trajectories in advance. The full body motion is split in a task and compensation motion. The task motion can be generated in advance, while the compensation motion is obtained during execution of the task. We show that the compensation motion can be obtained by making use of the linear relation between the joint velocities and the linear momentum of the complete robot. A setpoint for the linear momentum is generated by making use of the error between the current Capture Point and the desired Capture Point location. We have implemented the control algorithm in simulation as well on a real humanoid robot. We were able to create stable full body motion for a bending forward task. It turns out that the control algorithm to create stable full body motion is insensitive for model errors in the internal model of the robot.

Body powered prostheses have many advantages: They are reliable, lightweight and relatively cheap. The disadvantage is the need of a shoulder harness, which causes discomfort, pain and trouble donning and doffing the prosthesis. The goal of this thesis is to develop a body-powered prosthesis without the need for a shoulder harness. This is realized by making a design that uses passive wrist flexion of the prosthesis itself to operate the grasping mechanism. The force and displacement are converted to a grasping motion by using a hydraulic system. The grasping force is enhanced by a pressure intensifier and holding an object is achieved by including an automatic lock.

Laparoscopic surgery is a technique in which operations in the abdomen are performed with long slender instruments through small incisions (5-10 mm). Single port surgery is a form of laparoscopic surgery with possible advantages in which the surgeon operates almost exclusively through a single incision. In order to compensate for the limited freedom of motion of the used instruments, steerable instruments with articulating tips that can be steered in 2 DOF have been developed for use during laparoscopic or single port surgery. The freedom of motion provided by steerable instruments make single port surgery possible, but however introduces a number of problems (eye-hand coordination conflicts, incision widening). This paper presents the design of a new, multisteerable instrument that can be used for both laparoscopic as well as single port surgery.

To diagnose and treat colon cancer a colonoscopy is usually performed. Current colonoscopy is performed by advancing a colonoscope (scope) through the tortuous colon. However, the flexible scope often buckles when advanced. This can cause discomfort and pain for the patient and can make the examination of the colon difficult for the endoscopist. Guiding the scope, with an overtube that has a controllable rigidity, when the scope is advanced could reduce these problems. The rigidity of the overtube should be switched between a flexible state, that allows the insertion of the overtube, and a rigidified state that provides sufficient support to the scope. The PlastoLock overtube utilizes the glass transition of Purasorb© PLC 7015 (PLC). By changing the temperature of its PLC components from 43 to 5°C, the PlastoLock overtube is reversibly rigidified. A physical test model of the PlastoLock overtube shaft was developed and its stiffness at 43 and 5°C was determined. The tests showed a reliable, reversible and fast change in stiffness. The stiffness of the test model in flexible state is sufficiently low. However, the stiffness of the rigidified test model is insufficient. A larger change in stiffness was found when testing the test model submerged in water compared to passing water through the PLC components. The measured stiffnesses were considerably below expectation. Possible causes for this discrepancy were investigated, but require further testing to confirm. These future tests should also indicate whether the stiffness of the rigidified test model can be increased.

Static balancing is a useful concept to reduce operating effort in mechanisms. A statically balanced system which is designed to counterbalance a mass, is referred to as a gravity equilibrator. The potential energy in a gravity equilibrator is constant, which in most of the times is achieved by mechanical springs. Often helical springs are used, although these springs take a lot of space within the workspace of the mechanism. This paper presents the design of an adjustable gravity equilibrator using torsion bars, which saves space in the working area. Static balancing is achieved with a non-constant transmission (NCT). A new NCT design, and a general method to calculate the design parameters are presented. The stiffness of the torsion bars can be adapted by changing the active length. In this way it is possible to balance different masses with the same system.

Lifting patients is a demanding task for care providers. In addition, the number of patients is rising and the number of people with obesity is expanding. Current lifting aids are single purpose and time consuming to use. Exoskeletons can fulfill the demand for a versatile and easy to use lifting aid. A drawback of a typical exoskeleton is that in order to function correctly the axes need to be aligned to the human joints, which is time consuming. Furthermore, an exoskeleton for healthcare must reduce the reaction forces in the user while lifting. It is chosen to design an exoskeleton, which requires no adjustment and can cope with power enhancement. The goal of this paper is to design an exoskeleton that is fast, easy to use and reduces the reaction forces in the user. A design is proposed which easily fits different sized users. In addition the reaction forces in the human skeleton are eliminated. The model is tested by means of a demonstrator. Elastic tension elements are used as a gravity compensator. By reducing the potential energy fluctuation the required external input is reduced. Optimizing a number of design parameters leads to a calculated moment reduction of 98.8% and moment fluctuation reduction of 96.8%. This is the first exoskeleton to combine fast to use design with high-energy efficiency gravity compensation.

This thesis discusses the design of a new steerable tip for a laparoscopic instrument. A new tip design is required since current steerable tip designs have problems with the bending stiffness and the lifespan of the cables. Underaction is a main cause of the low tip stiffness. Since one of the design requirements is that the tip needs to be able to rotate in two perpendicular planes, the tip has two rotational degrees of freedom (DOF). The simplest way to fully actuate the tip and to rotate each DOF over 90 degrees in a clockwise (CW) and counter clockwise (CCW) direction is by using two cables for each DOF, resulting in a total of four cables in the tip. A limiting factor of the lifespan of the tip is the fatigue of the cables. The fatigue is the result of the cables being forced to make a sharp bend during a rotation of the tip. To reduce the fatigue of the cables, the cables therefore need to be guided and to make a bend as large as possible in a g5 mm tip. As a prove of concept, two prototypes have been produced. From these prototypes it can be concluded that each DOF in the tip is able to rotate up to an angle of 90 degrees in CW and CCW direction. It can also be concluded that the tip is fully actuated. The bending stiffness of the tip therefore only depends on the stiffness of the cables and the rigid bodies of the tip. Since the cables and rigid bodies will be produced from steel, the bending stiffness of the tip will be high. Considering the cables to have a diameter of 0.5 mm, the cables will be guided over a guiding with a radius of 3.48 mm. Compared to the EndoWrist, where the radius of the pulley with similar cables would be 2 mm, the radius is almost 1.75 as large. The result is that the lifespan of the cables in the new design will be superior.

Laparoscopic graspers require a high pinch force to generate sufficient friction force (grip) for tissue manipulation. Excessive or insufficient pinch forces distributed along the small contact area of laparoscopic graspers can cause damage and are one of the reasons why the risk of intraoperative complications during Minimally Invasive Surgery (MIS) procedures in the abdomen is 2-4 % higher compared to open surgery. The goal of this research was to develop and evaluate an 5 mm laparoscopic grasper, which has the same functionality (generated friction force, grasping time) as a conventional grasper for use on the intestine but which requires lower pinch force due to the use of adhesives. To lower the pinch force the adhesive component of the friction force was enlarged by introducing a muco-adhesive between tissue and grasper. To lower (local) high pressures a flat surface was used. Two experiments were conducted to find out in which direction the friction force generated by the adhesive film was the largest and to find the minimum required area of adhesive film to generate a force of 5 N. Next, a design for the tip and a design for the adhesive film feed mechanism was made. To evaluate the design a prototype was created, which was used to investigate whether the proposed tip design was able to generate a friction force of 5 N using a pinch force lower than 3 N. The prototype of the adhesive grasper was able to generate a friction force of 3.12 ± 0.58 N, while using a pinch force of 2.5 N. The generated friction force did not meet the goal of 5 N, but the concept of lowering the pinch force by introducing an adhesive layer is promising; the pinch force needed by the proposed tip is lower compared to existing graspers and the friction force was independent of the generated pinch force. The friction force can be increased further by developing a new adhesive film or by increasing the contact area.

During the surgery, the lighting unit often needs to be manually adapted. However, the manual manipulation may cause loss of concentration, loss of time and increased risk of infections. To improve the manipulation, a semi-automated lighting system commanded by the surgeon is suggested. The commands are given via a pointer device to indicate the desired location and orientation of the light beam. The pointer device is tracked in space with a low-cost infrared 6DOF real-time system based on Nintendo Wii-Remotes. In this study, the precision and accuracy of the tracking system was tested with static markers, dynamic markers and with the pointer device. Moreover, the wound reconstruction was evaluated. The results showed that the tracking system is sufficiently precise and repeatable. On the other hand, the position accuracy was lower than expectations, especially with the pointer device. It is concluded that the method of collecting relevant parameters with a pointer device using a low-cost tracking system is promising for the surgical lighting control application when a proper mapping of the system coordinates to the real world coordinates is achieved.

This paper presents the first zero stiffness six degrees of freedom (DoF) compliant precision stage. To deal with problems like backlash, friction and lubrication for performing ultra-precise positioning in a vacuum environment, a novel compliant structure is proposed. All six degrees of freedom are statically balanced (i.e. near zero stiffness) to balance the gravity force and cancel out the stiffness due to the compliant design of the structure. Cooperative action of post-buckling behavior of bi-stable beams and constant stiffness of v-shaped beams, arranged in three units in a triangular configuration, are proposed for out-of-the-horizontal-plane motions. The in-plane motions are achieved by three flexible rods loaded near their buckling load. An investigation on adjusting the design parameters to minimize the residual actuation force is also performed. A prototype was manufactured and finite element modeling was performed to evaluate the concept. Experimental evaluation showed that the design is successful: for the case study a gravity force of 34.4N was balanced with a residual stiffness of 1.75N/mm in a domain of 2mm for the out-of-plane translation, while the out-of-plane rotational stiffness was less than 18.5Nm/rad, caused by parasitic torsion of the bi-stable beams and v-shaped beams. The stiffness for in-plane translations and rotation was 0.4N/mm and 2Nm/rad, respectively. Near zero stiffness 6DoF positioning can thus be achieved. The novel mechanism or the principle may be extensively applied in several applications in precision engineering or in other relevant fields, such as vibration isolation.

This paper presents the idea to use a resonant mechanism to reduce energy consumption in robotic arms with repetitive tasks, such as pick- and place tasks.

Experimental research with human subjects on the effect of offering different types of haptic feedback to improve the human performance during a deep-sea mining task using a suspended grab.

Obstacles in the path of a running robot need to be avoided in order to avoid falling down. Currently, there are no control strategies that determine the appropriate step locations to obtain a successful overstep of an obstacle. The objective of this simulation study is to maximize the gap size by determining the step locations. The step strategy is tested on the SLIP-model and a model containing leg damping and push-off. With the means of an optimization, it is found that the optimal step strategy consists out of 3 phases: an adaptive phase from running cycle to the optimal state for the beginning of the leap, the beginning and end of the leap and another adaptive phase to end in a desired end state. For the SLIP-model is found that the maximum gap size is almost independent of the initial velocity of the model and mostly depends of the system’s energy. In order to maximize the gap size, the first and second step location have to be coincident. Furthermore, the damping and push-off proved to be an important factor for the step locations and the obtained gap size, as the first and second step locations do not coincident anymore and the gap size is reduced significantly.

This thesis analyses the range of motion of a resonating robotic arm under motor torque and time limitations and shows the beneficial effects it has on the speed of executing a pick and place task.

This thesis brings together, for the first time, the fields of energy harvesting and static balancing. The proposal of two new architectures for the design of mechanical oscillators is supported by an extensive review on the existing energy harvesters. For the first one, a statically balanced oscillator, an analytically study proved it to be ineffective. This pushed for the development of a statically balanced frequency up-converter, that can integrate an energy harvester capable of coping with low frequencies vibrations of broadband nature. On the static balancing ground, a new mechanism is proposed, with the balancing of the folded suspension, a traditional mechanism of precision engineering. Numerical analysis suggests that high quality balancing is achieved for a large amplitude of motion. A preliminary study is also executed, introducing bond graph modeling to the field of energy harvesting. Bond graphs are a natural representation for the cross-domain nature of energy harvesters, allowing an integrative view.