Background
An upper limb amputee currently has two choices for a body-powered prosthesis, a Voluntary Opening (VO) or Voluntary Closing (VC) hand prosthesis. Which type is best, depends on the task and the individual. Currently, there are no good options for VO and VC in one design.
Objectives
To design a proof-of-principle of a hand prosthesis and to validate the feasibility of the prosthesis. The hand prosthesis must have two different modes, the VO mode and the VC mode. Changing between these modes can be done without using the other hand..
Methods
First, a list of requirements and wishes was made, where cable forces are important because too much cable force can cause discomfort, fatigue or make the prosthesis difficult to control.
A new design was created and a prototype was built for user testing. SHAP was used as the outcome measure.
Results
The prototype allowed the user to change between VO and VC and SHAP showed promising Linear Index of Functionality (LIF) values. The calculated cable forces were mostly within the requirements. However, because the prototype of this design was produced with an FDM-printer, not all the tests could be done and the calculated forces could not be verified.
Conclusions
A prototype of a hybrid hand prosthesis with VO and VC modes showed promise, with positive test results. However, limitations in the prototype's construction hindered some tests. The calculated cable forces mostly met requirements, except for a slightly high pinch grip force. Further development is needed, and there are material and design recommendations. This concept demonstrates feasibility but requires more work to become a functional hand prosthesis.

Introduction: Amputees still experience problems with the use of their upper limb prostheses, mainly in the lack of comfort and functionality. This results in rejection of the prosthesis or overuse injuries due to compensatory movements. The comfort and functionality should be improved by reducing weight and increasing the degrees of freedom. The wrist is an important joint for increasing the mobility. And for reducing the weight, another actuation method than the most available and heavy electrically driven device should be used. Methods: This study designs a hydraulic curved cylinder for the application of a wrist joint. Because of the complex and curved shape the manufacturing method used is 3D printing. The functionality of three 3D printing methods (FDM, MJF and SLA) and three sealing techniques (O-ring, X-ring, and Conus) will be evaluated by testing the amount of friction and leakage to find which configuration performs best and whether it results in an efficient actuator. Results: The SLA-cylinders and the Conus allowed the least leakage. The combination of these two even resulted in zero leakage. For friction the SLA and FDM-cylinders performed equally, only the MJF-cylinder caused more friction. The SLAcylinder is the only cylinder that can hold a constant pressure without leakage for 5 out of 8 pistons, when a 4 kg weight is attached. Finally, only piston-cylinder combinations with piston O-25 or Cylinder X.MJF do not match the requirements for the maximum allowed leakage and adjustment torque. Conclusions: The piston-cylinder combination of SLA-parts and Conus perform the best. For the application of a wrist joint in prostheses more research needed for the repeatability, scalability and long-term performance.

Background Upper limb prostheses help people with an upper limb deficiency in performing activities of daily living. They can be divided into two categories; body-powered and externally powered prostheses. The advantage of body-powered prostheses is that they provide feedback to the user. The advantage of externally powered prostheses is the low operating force required to control the prosthesis. To reduce rejection rates of upper limb prostheses control, cosmetics and comfort should be improved. To improve control, a design was proposed integrating proprioceptive force feedback into an externally powered upper limb prosthesis with a haptic interface placed on the scapula. However, the cosmetics and comfort are to be improved. The goal of this study is to design a haptic force feedback system that meets the demands regarding comfort and cosmetics. Method Design requirements and mechanical requirements are set. A conceptual design was made using SolidWorks and a prototype was built. The proposed prototype was tested on a test bench to evaluate the overall system. It was analyzed whether the design met the pre-set requirements and the results were compared to other devices. Results The designed haptic device is made out of an anchoring system, pneumatic artificial muscle (PAM), and a distance sensor. The total weight of the system is 41푔 for the anchoring system and PAM, and 29푔 for the distance sensor. The dimensions are 50푥25푥120푚푚. The maximum pressure for the actuator is 3푏푎푟. The output forces reached are 87.41푁, 79.04푁, 100.00푁, 85.38푁, and 104.8푁 for actuators with an initial length of 80푚푚, 90푚푚, 100푚푚, 110푚푚, and 120푚푚 respectively. The designed distance sensor measures a distance up to 58푚푚, with an accuracy of ±1푚푚. Compared to other devices the developed overall system is lighter in weight and smaller in size. Furthermore, it is made out of flexible materials, allowing the device to bend along the curve of the shoulder. Conclusion This study presents a new design for a haptic interface to provide proprioceptive force feedback for an upper limb prosthesis. It is an improvement in cosmetics and comfort, while still meeting the mechanical requirements. Future research should be done with users of an upper limb prosthesis to evaluate the applicability.

Many patients with an upper-limb deficiency choose not to wear their prosthetic devices due to a multitude of reasons, including physical discomfort and unintuitive, cognitively demanding control methods. A new haptic interface was developed combining the desirable control characteristics of body-powered control prostheses with the comfort of an externally powered prosthesis. A study (n = 10) was performed on the effect of the haptic feedback provided by the interface in a stiffness perception task. Participants were asked to determine the stiffness of a object with and without visual and/or haptic feedback. The haptic feedback was provided through the newly developed interface and the visual feedback through the display of a virtual slave. Results indicate that there is no significant difference in stiffness perception between the conditions with visual and/or haptic feedback.

Patients who suffer from Duchenne Muscular Dystrophy, have to live with hand impairments for over 15 years. This significantly influences their ability to live independently. Currently, static splinting interspersed with stretching of the hand is the course of treatment for this patient group and developed active hand orthoses focus mainly on stroke and SCI patients. The Symbihand was developed by R. Bos and K. Nizamis in 2019. The active hand orthosis is especially designed to assist DMD patients in ADL. Control is intuitive, the self-aligning mechanism prevents inaccurate joint alignment during flexion and the hydraulic finger modules are forceful and can achieve proper ROM. One of the limitations of the device is that the thumb is restricted to an awkward position in order to facilitate grasping abilities. That while, the thumb is of substantial influence on the versatility of the hand and actuation of this digit could be of additional value for functionality by adding the possibility of the key pinch . This thesis describes the design and evaluation of a thumb module for the Symbihand with the aim to release the awkward static position of the splinted thumb. In order to add a thumb module to the system, preservation of the hydraulic actuation and the self-aligning mechanism is imperative. The design scope of the thumb module becomes as follows: "The design of a hydraulic thumb module for the Symbihand, with the focus on functional assistance of DMD patients who have limited hand function and are wheelchair confined." This can be achieved by assisting the hand in the ROM and force needed for the precision pinch, lateral pinch and cylindrical pinch. It should be taken into account that the addition of a thumb module might complicate control, so added function and diminished ease of control must be in balance. Included in this thesis is a design paper about the thumb module (Section II), a literature study on the fixture design of hand orthoses for DMD patients (Section III) and additional explanations of design choices and requirements in the Appendix.

For patients with a hand disability, hand exoskeletons can improve their ability to perform activities of daily living.
Its complicating that on the hand little space is available to build an exoskeleton. So, moment arms of actuators must be small. This complicates generating adequate moments. Strong actuators may be a solution, but they add weight, which should be minimized for comfort. The goal of this thesis is to design a proof of concept that improves force output, considering weight and size criteria.
The proof of concept divides the function of the exoskeleton into two phases that work one after the other. In the first phase the fingers flex to encapsulate an object, in the second phase force is applied. Each phase has an actuator that suits its requirements.
Results show that force output equals 5.087 [N], while the system weights 49.9 [g]. This equals a force-to-weight ratio of 102 [N/kg].
Force output was lower than theorized due to a variety of reasons and did not meet the set criteria of 10 [N]. The criteria of size were not met at the dorsal side of the proximal phalanx. The criteria were 20 [mm] extrusion, 27 [mm] was the end result. Both failures are expected to be solvable. It is concluded that with updates, the design can improve force output while maintaining a small and lightweight design.

Lower limb exoskeletons enable paraplegic patients to stand-up and walk again. However, the weight and overall functional performance of the exoskeleton prevents them from being widely used. To reduce the weight and increase
the performance, pneumatic actuators can be used as an alternative to the commonly used electromechanical actuators. This thesis presents a new pneumatic actuator design to power a lower limb exoskeleton in daily life
activities. The goal of this thesis is to take a step towards the design and development of exoskeletons with reduced weight, increased compliance and that enable paraplegic patients to perform daily life activities. Out of several
concepts, a single vane rotary actuator is worked out in more detail and a prototype is manufactured. This actuator is able to generate a peak torque of 96 ± 2 [Nm] at an operating pressure of 12 [bar], has a range of motion of
132 ± 1 [°] and is able to generate a peak angular velocity of 430 ± 5 [°/s] and a peak power of 252 ± 3 [W]. The designed actuator has a width of 165 [mm], a length of 135 [mm], a dept of 54 [mm] and a total mass of 2.3 [kg], but
with small changes can be decreased to below 1.6 [kg]. This is the first known pneumatic actuator able to generate sufficient dynamics to power a full mobilization lower limb exoskeleton in daily life activities. It can be concluded
that this new design is a promising actuator to be used in lower limb exoskeletons. In further work, the bandwidth of the actuator must be determined accurately.

Nowadays the design of prosthetic hands is mainly focused on myo-electric control for more functionality. And easy producible 3d printed prosthetics to lower the costs of a custom prosthesis. As a result of this change of focus, the body powered prosthetic hands currently on the market are mainly simple clamping mechanisms with no innovative functions. Looking back into the history of hand prosthetics many body powered prosthetic hands housed a couple of innovative design choices to increase the functionality. Some examples of this are the Pringle-Kirk arm and the Despinasse hand. As a counter reaction to this movement, a new body powered prosthetic hand is designed. The new prosthetic hand will be based on the innovative solutions of the past and will bring back more functionalities to the body powered prosthetics. The new design housed fingers made out of cylindrical springs, in combination with leaf springs. This is all actuated via a dependency mechanism in the hand palm, this combination allows for very flexible fingers that can grab complexly shaped objects and still offer a multi finger grip. The first tests revealed that the leaf springs limited the motion of the fingers and further testing without the leaf springs showed a setup with only cylindrical springs was a better solution. The second test was focused on pinch force, although the maximum acquired pinch force was not high, a sturdy grip should be possible based on literature, this does need further testing to validate. For the continuing of the prototyping testing of the dependency mechanism was done, initial testing at a larger scale showed promising results, little to no loss of force. The conclusion that can be drawn based on these tests is that there are certainly parts of prosthetic hands of the past that are worth taking a closer look at.

Hand prostheses commonly advertise on three main selling points: strength, speed and lightweight. Most conventional hand prostheses are only able to combine two of these three attributes. Therefore, combining all three attributes into a single device can result in a commercially attractive hand prosthesis. Another interesting point, particularly for pneumatic prostheses, is the usage time, as historically many have run into problems here and an extended usage time makes it attractive to the user. The goal of this graduation research is, therefore, to design a pneumatically powered hand prosthesis, that combines a high grip strength, a high opening/closing speed and lightweight into a single device, whilst maintaining a reasonable usage time. A hybrid actuated hand prosthesis is designed that combines a finger design based upon the Delft Cylinder Hand, with dual-mode actuation. This dual-mode actuation increases the efficiency of the hand and consist of a CO₂ supply with a hydraulic transmission to the fingers. A final prototype of the dual-mode actuation transmission is fabricated and evaluated. Although there is room for improvement in the resistance and timing of the system, the hand has a relatively high pinch force of an estimated 56 N. Furthermore, a grip speed of less than a second makes the hand attractive to be used. With a mass of only 235 grams, the hand weighs less than most of its competitors and is comfortable in use. The dual-mode actuation significantly increases the efficiency of the hand and gives it a usage time of over 400 cycles.

Body-powered prosthetic hands used by below-elbow amputees function in two phases. There is the opening and closing motion of the hand (Motion Phase) and the phase when the hand is in contact with an object, and the fingers apply a pinching force (Pinching Phase). Each phase requires a different set of dynamics to properly function. In the Motion Phase, a small amount of applied force must result in a large translation of the fingers, in the Pinching Phase a small amount of force must result in a large pinching force and a small translation. The problem is that body-powered prostheses have fast motion given a low force input during the motion phase but cannot achieve a high pinching force with a low force input during the pinching phase. The goal of the project is to design a mechanism that passively switches between the dynamics of the motion phase and pinching phase for body-powered active closing hook prostheses. In the motion phase a small force input must result in a large output translation and in the pinching phase a small force input must result in a larger force output and a small output translation. In the motion phase a minimum cable force of 10 N is required and in the pinching phase a pinching force of 30 N must be achieved with an input force of 40 N or less The prototype consists of a hydraulic telemanipulation system with a master (shoulder), operated by the shoulder harness, and slave (hand), operates the hand prosthesis, cylinder connected to each other via a booster mechanism. The booster is inactive in the motion phase and active in the pinching phase. The results show that in the motion phase an input force of 5 N can perform the full translation of the prosthesis. If the hand is met with resistance the input 5 N input can increase up to 24 N until the pinching phase activates. The translation in the pinching phase is too small to observe any change. The pinching phase activates at a pinching force of 12 N and an input force of 24 N. In the pinching phase the pinching force reaches 35 N with an input force of 32 N input force. The dynamics of the phases show to be unaffected by different object stiffnesses and lowering the activation force of the pinching phase only shifts the pinching phase along the motion phase. In conclusion the 5 N minimum input force is too low. An input force below 10 N result in inferior control for the user. In the pinching phase an input force of 32 N can reach a pinching force of 35 N, which meets the set requirements of 30 N pinching force with an input force of 40 N or less. A larger translation is required in the pinching phase to compare the translation dynamics between the motion and pinching phase. More research is required to properly define the desired activation force, how much translation is required in the pinching phase, and to find optimal spring properties for the return springs in the hydraulic cylinders.

The WILMER appealing prehensor is a body-powered (BP) prosthesis for people with a trans-radial upper limb deficiency, which is highly appreciated because of its outward appearance and functionality. Currently, prehension of the WILMER appealing prehensor is voluntary opening (VO). Voluntary closing (VC) prehension could offer the prosthetic user some clear advantages, especially equipped with a locking mechanism. A VC controlling mechanism is designed and evaluated in order to provide prosthetic users a VC version of the WILMER appealing prehensor. Furthermore, an adequate locking mechanism is searched for. A final prototype of the VC WILMER appealing prehensor is evaluated. By preserving the outline of its VO equivalent, a high appreciation for its outward appearance is secured. With a mass of only 99 gr, the VC WILMER appealing prehensor is comfortable to wear. The terminal device has an adequate opening width of 53.5mm, enabling its prosthetic users to grasp a wide variety of objects. The hysteresis of one cycle of the VC WILMER appealing prehensor is very low, indicating that the terminal device is very efficient. Preliminary
results show that there is room for improvement regarding the cable operating force and locking mechanism. At larger apertures the cable operating force necessary to get an adequate grip force slightly exceeds comfortable limits. The VC WILMER appealing prehensor is equipped with the vertical mount Sure-Lok.
Although the vertical mount Sure-Lock is a more effective locking mechanism than locking mechanisms tested in literature, the drop in grip force induced after activation is still quite large.

Prostheses are challenging to obtain in low-income countries due to a lack of experts, remote locations, unfortunate production circumstances and an inadequate amount of research. A 3D printed WILMER open fitting for transradial amputees has been developed, which can solve this problem. It is entirely 3D printed and connects the prosthesis to the residual limb. However, the current design is not breathable nor volume adjustable. This is a significant obstacle since the residual limb perspires and dilates/diminishes during the day.
Therefore, the aim of this paper is to design a breathable, volume adjustable, parametric, 3D printed socket for transradial amputees in low-income countries.
This new design consists of straps connected with hinges which improve the range of motion. The material used for the socket is TPU 95A. The straps are perforated to improve the breathability of the socket. Furthermore, a clickable spacer, which is strong enough to withstand a force of 200 N, is attached to make the socket volume adjustable. The complete socket is also subjected to strength tests which resulted in a maximum manageable force of 100 N, attached to the prosthetic hand. However, the socket has not been evaluated by patients, which means that real-life wearing conditions are not achieved. Therefore, it would be a recommendation for future research to examine the socket on patients. Overall, this study provides the design of an affordable, comfortable, aesthetically pleasing, durable, parametric socket for amputees in low-income countries.

A large proportion of upper extremity prostheses are abandoned by their users.
Commonly, the main reasons for abandonment are related to comfort, control and cosmetics.
Prostheses are often experienced as too heavy and have limited functionality.
A pneumatic power source is able to provide a relatively high force using a small and lightweight actuator.
However, state-of-the-art pneumatically powered upper extremity prosthesis offer either high grasp forces or the ability to adapt to the size and shape of an object.
This article presents the design of a pneumatically powered hand prosthesis for toddlers, which focuses on being lightweight and highly functional.
An underactuated 3-DOF linkage-based finger transmission mechanism was created and served as a proof-of-principle.
The resulting prototype was 3D printed and tested following an elaborate list of criteria.
The results demonstrate that the mechanism is capable of transmitting an actuator force of 100.5 N to a fingertip force of 32.3 N using 5 bar of pressure.
The proposed mechanism also offers the functionality of adaptive grasping.
The conceptual design and prototype show promising capabilities for the development of a lightweight and highly functional prosthesis for toddlers.

Background Despite its high demand, prostheses are too often abandoned because they fail to meet the main requirements control, comfort and cosmesis. Body-powered hook prostheses provide good control due to their proprioceptive feedback but are in general not efficient nor appealing. The WILMER group has developed an appealing voluntary-opening prehensor by building all mechanical parts inside the prosthetic cover. The voluntary closing (VC) version, the Tweezer, has slight advantages over the voluntary opening but failed to provide sufficient energy transmission within the available space to which hydraulics offer the solution. The objective is to develop and evaluate a hydraulic VC mechanism within a body powered hook prosthesis that meets the main requirements. Methods A hydraulic system was designed. The system shall transmit a 32 N and a 6.4 N actuation force, when holding objects for a prolonged time, to a 7 N pinch force. A maximum 40 mm actuation displacement shall close the hook from a 50° open to a 0° closed position. The system shall fit inside the prosthetic cover and have a maximum mass of 43 g. A prototype was built and tested to measure its performance. Results The design consists of three hydraulic actuators: a master cylinder, a slave cylinder and a pressure intensifier. The user actuates the master cylinder, which is incorporated in the harness, causing fluid to be transferred to a slave cylinder in the prosthesis that closes the hook to grasp objects. When an object is met the pressure intensifier amplifies the pressure of the slave to increase the pinch force to 45 – 53 N and 9 – 11 N for actuation forces 32 and 6.4 N respectively. The actuation displacement equals 26 mm. The prototype failed to be manufactured properly within the given time and a simplified version, equal to the inactive pressure intensifier, has been made to prove part of the concept. Theoretically, the simplified version closes the hook with an actuation displacement of 11 mm and reaches pinch forces of 5 – 6 N over the hook range. The prototype closes the hook with 12 mm and reaches pinch forces 3 – 5 N. It takes 4 N to reopen the hook. The simplified version weighs only 15 g and fits easily inside the prosthetic cover. The mechanism provides proprioceptive feedback at the master cylinder. Conclusion Part of the concept has been proven. Theoretically, by adjusting the simplified versions parameters the 32 N actuation force could generate pinch forces 16 – 19 N with a 34 mm actuation displacement. It would outperform other body powered prostheses in terms of force transmission. The hydraulic VC mechanism has the potential to transfer a comfortable actuation force and displacement into the required pinch force within the available space of the Tweezer. Thus, a voluntary closing hook prosthesis is designed that can satisfy all user requirements control, comfort and cosmesis.

This thesis studies the possibility of energy increase in tape-spring assemblies through stacking, defined as the practice of placing tape-springs on top of each other in parallel. consists of five chapters. Chapter 2 consists of a paper that presents a theoretical approach to stacking of tape-springs, and studies the potential of energy storage using analytical functions of tape-spring strain energy and deformation behaviour. The goal of this simplified approach is to understand the potential of energy increase through stacking, and subsequent material considerations, without taking practical considerations in account yet. This creates context for the next chapter, in which a more specific configuration is further worked out. Chapter 3 consists of a paper with a simulation and experimental approach on energy increase in tape-springs, considering a specific configuration of boundary conditions, comparable to an arm support system. The goal of this paper is to verify the energy storage increase for a practical implementation of a stack of tape-springs. The strain energy distribution in the material and the resulting force-deflection behaviour is studied in a finite element shell model in MATLAB. The force-deflection behaviour of a stack of two tape-springs is experimentally validated, and compared to the force-deflection behaviour of the individual tape-springs. Chapter 4 contains the general discussion of the findings for both the theoretical, as well as for the simulation and experimental approach to the stacking of tape-springs. The main findings are highlighted in chapter 5. Some additional information on this thesis is added in the appendices.

Introduction: Almost 57 percent of above elbow amputees stop using their prosthesis. One of the main factors of non-wear is the high weight. Pneumatic actuation can be more lightweight than electronic actuation, and might therefore help with reducing the mass of a prosthesis and increase its comfort. To illustrate this potential, the goal of this thesis was: "To show the potential of pneumatic prostheses by designing a lightweight pneumatic elbow prosthesis, with a functionality equivalent to existing prostheses". Methods: The design process was divided into five phases: Analysis, Conceptualization, Embodiment, Manufacturing and Assembly, and Testing. The analysis brought to light the functions, requirements, wishes, and design values. The two design phases, conceptualization and embodiment, translated these into a potentially viable prosthesis. Afterwards, a prototype was manufactured, assembled, and tested to see if the functions, wishes, and requirements were met. Results: The prototype weighs almost 1300 [g]. A payload of 4.0 [kg] can be lifted to 87 [°]. In theory, 2.5 [kg] can be lifted throughout the entire range of motion, up to 140 [°]. The maximum pronation/supination torque is over 2.8 [Nm] throughout the entire range of motion of ± 90 [°]. The locking mechanism is theoretically capable of passively holding over 6 [kg] in any position. In theory, an average of 125 cycles can be achieved per 25 [g] CO2 cartridge. Discussion: The prototype does not have an integrated fuel source. The weight of the prototype exceeds the maximum by almost 280 [g]. Switching to electronic control significantly decreases the prosthesis mass. The frame of the prototype was under-constrained, leading to an increased friction for higher angles of flexion. Conclusion: The combination of the high functionality and low mass of the prototype shows potential for pneumatic actuation for prostheses.

Aim: This project aims to design a lightweight, inexpensive and easy to use upper arm prosthesis through improving the design of ARM3D, which is a 3D printed body-powered transhumeral arm prosthesis. This study will cover general shortcomings of body-powered arm prostheses as the weight, cost, amount of parts and limited accessibility of them. This study also focusses on a natural appearance of the prosthetic arm. Results: The improved design of ARM3D is made of six 3D printed and eight non-3D printed parts. It has three Degrees of Freedom (DOF’s), one control cable, a harness both to suspend and control the prosthesis, an active voluntary closing hand, a passive rotating wrist joint and a passive elbow hinge joint. The prosthesis costs €59,68 and weighs 403 g. It takes 3 days, 6 hours and 47 minutes to print and 15 minutes to assemble. The maximum open hand width is 64 mm and the prosthesis needs 15 N of tension force on the control cable to operate. Furthermore, it is possible to paint the prosthetic fingernails and to remove the nail polish. Conclusion: An improved design of the ARM3D prosthesis is presented in this paper. ARM3D is almost entirely 3D printed. It is a lightweight and inexpensive device. A field study is required to gather more information whether the prosthesis is easy to use.

Current upper-limb prostheses are often rejected as a result of high activation forces that are needed for control. Another reason for rejection is the absence of appropriate proprioceptive feedback. In this study, a pneumatic control system was designed that decreased the activation forces and where proprioceptive feedback was provided. The system was placed on the back of the user and was actuated by shoulder movements. The design has been evaluated on two aspects, namely the sensitivity, determined by the Just Noticeable Difference (JND) and the Weber Fraction (WF), and the displacement (re-)production accuracy (e.g. opening/closing of the prosthetic hand). Ten healthy, right-handed male subjects performed both experiments. The sensitivity was assessed by a reminder task where two forces were compared. Four reference force levels were used: 2, 4, 6, and 8N. This resulted in WF values of: 18% for 2N, 4% for 4N, 3% for 6N, and 2% for 8N. The results for the three higher forces agreed with literature. To evaluate the displacement accuracy the Absolute Displacement Error (ADE), the Relative Displacement Error (RDE), and the Displacement Variability (DV) were measured for three different reference displacements: 5mm, 10mm, and 20mm. The results show that the control of the system is accurate enough for object manipulation and the relative error was lower than 1% for each reference displacement. This design may be the next step in controlling prosthetic hands.

In Chapter 1, the focus is on the classification of force generators, which is the family of mechanisms to which balancers belong to. The goal of this chapter is to introduce a bottom-up classification method to identify the complete solutions space of transmissions in force generators based on their transfer function. Using this method, spring-to-mass balancers with one non-auxiliary revolute joint will be classified to identify their working principles and find new design opportunities.

In Chapter 2, the focus is on balancers applied in exoskeletons and robotic manipulators. The goal of this chapter is twofold. The first goal is to introduce the optimal balancer adjustment types for application in exoskeletons and robotic manipulators. The second goal is to compare their performance based on the balancing quality, energy involved in adjustment and dimensions through an analytical MATLAB model. The introduced adjustment types incorporate a commercial available spring with realistic properties and their performance is considered in their complete range of motion.

The results of the complete thesis research are discussed in Chapter 3, and in Chapter 4, the main conclusions are highlighted. This thesis ends with additional information about the performed research, which can be found in Appendices A to H.

Upper limb amputees, using a body-powered prosthesis, generate energy with their shoulders which leads to opening or closing of the prosthesis. The preference for one of these types, voluntary opening (VO) or voluntary closing (VC), differs for individuals and for task specifics. Research is, therefore, done regarding terminal devices which provide both types. Earlier presented hybrid devices are heavy, do not provide mechanical advantage or present a difficult switching procedure. A novel VO/VC device was presented, with the promising features of easy switching and good mechanical performance. However, in user tests this device did not perform well, mainly because of its finger shape.
The goal of this study is to improve the grasping performance of the VO/VC device. Changing fingers did not create a device which could fulfil all the requirements. Instead, another idea was embodied, prototyped and tested.
This device is able switch between VO and VC, by the use of two separate pivot points. Switching between the two is done with a bi-stable mechanism, which is activated by the intact hand. Results show that the device can be used in both modes and that users are able to switch with the bi-stable mechanism, but the mechanical properties do not meet the requirements. Additionally, the device performs less than expected on the user test, due to the bad mechanical properties and misalignments in the 3D-printed prototype. The device created is a good proof of principle for using two pivot points to shift between VO and VC. However, the bi-stable mechanism did not function as expected and a lot of friction is present leading to high forces in the cable. It is recommended to change the material, focus on using other springs which allow for larger opening widths and generate less friction and change the switching system to increase usability and safety.