Rino Versluys

Prosthetic feet: State-of-the-art review and the importance of mimicking human ankle–foot biomechanics

Numerous prosthetic feet are currently on the market for individuals with a transtibial amputation, each device aimed at raising the 3C-level (control, comfort and cosmetics) with slightly different characteristics. In general, prosthetic feet can be classified into three categories. These are, following the time line: conventional feet (CF), energy-storing-and-returning (ESR) feet and the recent so-called ‘bionic’ feet. Researchers have shown enhanced performance properties of ESR feet compared with early CF. However, even with the advanced technology, none of the ESR feet is capable of significantly reducing energy cost of walking or enhancing prosthetic gait (Nielsen et al. J Prosthet Orthotics 1989;1:24–31; Waters et al. J Bone Joint Surg Am 1976;58:42–46; Torburn et al. J Rehabil Res Dev 1990;27:369–384). From the 1990s, gradually more attention has been paid to the incorporation of active elements in prosthetic feet as the passive devices are not capable of providing the individual with sufficient ankle power during gait. Most part of the ‘bionic’ devices are still on the research level nowadays but one can expect that they will become available on the market soon. In this article, the evolution of prosthetic feet over the last two decades is reflected. The importance of mimicking human ankle–foot biomechanics with prosthetic feet is briefly discussed. Prior work in both objective and subjective evaluation of prosthetic gait is reported.

A biomechatronical transtibial prosthesis powered by pleated pneumatic artificial muscles

Due to its high power-to-weight ratio, a pleated pneumatic artificial muscle (PPAM) offers an interesting alternative actuation source for robotic devices. Its inherent compliant behaviour excites another broad field of interest: assistive clinical devices such as powered exoskeletons and prosthetics. In this paper, the design of a pneumatically powered transtibial prosthetic device is presented. A first prototype has been built and provides a preliminary test bed for control algorithm development and testing with able-bodied subjects in laboratory conditions. The characteristics and working principle of a PPAM are described. The design specifications and the mechanical model of the prosthesis are discussed. The mechanical design and the control structure are outlined. Furthermore, some initial walking trials with an able-bodied subject wearing the prosthesis prototype are presented and discussed.

The Safety of a Robot Actuated by Pneumatic Muscles—A Case Study

In situations where robots share their workspace with humans, and where physical human-robot interaction is possible or even necessary, safety is of paramount importance. This paper presents a study of the safety of a lightweight robot actuated by pneumatic muscles. Due to its low weight, it has excellent hardware safety characteristics. In spite of this, it is shown that the system can be unsafe when under PID control. It is also shown that safety can be greatly increased by using Proxy-Based Sliding Mode Control (PSMC). The role of passive compliance in safety is also investigated. It is argued that passive compliance can have positive as well as negative effects on robot safety, depending on the situation.

Successful Preliminary Walking Experiments on a Transtibial Amputee Fitted with a Powered Prosthesis

This paper presents the results of preliminary walking experiments on a transtibial amputee wearing a powered prosthesis. The prosthesis prototype serves as a proof-of-concept implementation for investigating the potential of pleated pneumatic artificial muscles to power a transtibial prosthesis. The device is equipped with pleated pneumatic artificial muscles, and tethered to a laboratory pressure source. The prosthesis is capable of providing the amputee with 100% of the required push-off torque and it can adapt its joint stiffness to the walking speed. This study supports the hypothesis that a powered transtibial prosthesis with adaptable stiffness might be beneficial to the amputee.

Reliability‐based design optimization of computation‐intensive models making use of response surface models

Design optimization can be very time-consuming depending on the complexity of the model to be optimized. This manuscript describes the development of an adaptive response surface method for reliability-based design optimization of computation-intensive models, capable of reducing optimization times significantly. The method applied in this paper makes use of adaptive response surfaces for the elements of the considered objective function and probabilistic constraints. Because the optimization takes place on the response surface and not on the complex model itself, the number of function evaluations is reduced significantly. Higher order response models are used in combination with the adaptive approach. Additionally, the order of the interpolating functions can increase during successive iteration steps before the optimized design parameter values are achieved. The response model to be optimized is not built from a pre-defined number of design experiments, as is done usually, but is adapted and refined during the optimization routine. The proposed optimization technique is evaluated on a finite element reliability-based design optimization with multiple parameters. Copyright

Orthopaedic rehabilitation: A powered elbow orthosis using compliant actuation

This paper reports on the powered elbow orthosis for orthopaedic rehabilitation project and its main challenges. The mechanical design is briefly discussed. The actuator being used is the novel rotational actuator, MACCEPA or Mechanically Adjustable Compliance and Controllable Equilibrium Position Actuator. The schematic representation and working principle of this actuator are recapitulated in short before describing the mathematical model of the orthosis and the choices made to find a balance between simplicity, usefulness and correspondence with reality.

Powered ankle-foot system that mimics intact human ankle behavior: Proposal of a new concept

This paper reports on the importance of understanding the human walking biomechanics for the design of new robotic and/or prosthetic feet. On the basis of the human ankle behavior, the design specifications for a new ankle-foot system are determined. Two existing electrically powered anklefoot concepts are described. The first device was developed at the Massachusetts Institute of Technology (MIT) Media Laboratory, the second was developed at Arizona State University. The performance of both devices is presented. Furthermore, we propose a new concept based on the MACCEPA. The working principle and the performance characteristics of this new system are discussed.

Successful walking with a biologically-inspired below-knee prosthesis

In this paper, we present the results of walking experiments with a below-knee amputee fitted with a biologically-inspired prosthesis. The design of the prosthesis is described together with the characteristics and working principle of its actuators. First experimental results with an amputee are presented that demonstrate the encouraging performance of the prosthesis in restoring ankle torque to the user during level walking.

A study on the bandwidth characteristics of pleated pneumatic artificial muscles

Pleated pneumatic artificial muscles have interesting properties that can be of considerable significance in robotics and automation. With a view to the potential use of pleated pneumatic artificial muscles as actuators for a fatigue test bench high forces and small displacements, the bandwidth characteristics of a muscle-valve system were investigated. Bandwidth is commonly used for linear systems, as the Bode plot is independent of the amplitude of the input signal. However, due to the non-linear behaviour of pleated pneumatic artificial muscles, the systems gain becomes dependent on the amplitude of the input sine wave. As a result, only one Bode plot is insufficient to clearly describe or identify a non-linear system. In this study, the bandwidth of a muscle-valve system was assessed from two perspectives: a varying amplitude and a varying offset of the input sine wave. A brief introduction to pneumatic artificial muscles is given. The concept of pleated pneumatic artificial muscles is explained. Furthermore, the different test methods and experimental results are presented.

On the development of a powered prosthesis for transtibial amputees

This paper reports on the development of a powered transtibial prosthesis. The initial prosthesis prototype is a pneumatically powered system, which serves as test bed for proof-of-concept and evaluating control algorithms in laboratory conditions. The characteristics and working principle of the actuators are described. The control approach is discussed. First experimental results with an amputee are presented that demonstrate the promising performance properties of the powered prosthesis.