Automatic ball balancing is a technique adopted in rotordynamics to reduce unknown rotor unbalanc... more Automatic ball balancing is a technique adopted in rotordynamics to reduce unknown rotor unbalance automatically. This technique sounds appealing as it can ease a panoply of balancing issues considerably. The presence of stiction, however, scatters consistent qualitative balancing and led to a limited implementation in the industry. Temporary speed reduction, a recent technique, could be used as a countermeasure for the stiction-induced scattering. Presented in this paper is an in-depth study detailing how the technique should be implemented to guarantee effective balancing. By analysing a rotordynamic model of the Jeffcott kind, the influence of a multitude of parameters is studied such as the initial mass positions, the initial unbalance, the adopted speed profile, shaft damping, stiction and the speed reduction plateau of the adopted speed reduction strategy. The main findings of the study are that the adverse effects of stiction can be contained considerably using the speed redu...
Typical rotating machinery drive trains are prone to torsional vibrations. Especially those drive... more Typical rotating machinery drive trains are prone to torsional vibrations. Especially those drive trains that comprise one or more couplings which connect the multiple shafts. Since these vibrations rarely produce noise or vibration of the stationary frame, their presence is hardly noticeable. Moreover, unless an expensive torsional-related problem has become obvious, such drive trains are not instrumented with torsional vibration measurement equipment. Excessive levels can easily cause damage or even complete failure of the machine. So, when designing or retrofitting a machine, a comprehensive and detailed numerical torsional vibration analysis is crucial to avoid such problems. However, to accurately calculate the torsional modes, one has to account for the penetration effect of the shaft in the coupling hub, indicated by the shaft penetration factor, on the torsional stiffness calculation. Many guidelines and assumptions have been published for the stiffness calculation, however,...
Turbomachine rotors, supported by little damped rolling element bearings, are generally sensitive... more Turbomachine rotors, supported by little damped rolling element bearings, are generally sensitive to unbalance excitation. Accordingly, most machines incorporate squeeze film damper technology to dissipate mechanical energy caused by rotor vibrations and to ensure stable operation. When developing a novel geared turbomachine able to cover a large power range, a uniform mechanical drivetrain needs to perform well over the large operational loading range. Especially, the rotor support, containing a squeeze film damper and cylindrical roller bearing in series, is of vital importance in this respect. Thus, the direct objective of this research project was to map the performance of the envisioned rotor support by estimating the damping ratio based on the simulated and measured vibration response during run-up. An academic test rig was developed to provide an in-depth analysis on the key components in a more controlled setting. Both the numerical simulation and measurement results exposed...
2009 IEEE International Conference on Rehabilitation Robotics, 2009
Rehabilitation robotics is a young discipline that will become an imperative when the age of the ... more Rehabilitation robotics is a young discipline that will become an imperative when the age of the population will keep rising. The orthopaedic rehabilitation of the elbow joint poses some interesting challenges. The elbow joint itself has some particular characteristics that render the rehabilitation process different from others. The mechanical design of the developed powered elbow orthosis using MACCEPA actuators will be briefly discussed, as well as the mathematical model of the system.
Proceedings of the 2005 IEEE International Conference on Robotics and Automation
This paper reports on the control structure of the pneumatic biped Lucy. The robot is actuated wi... more This paper reports on the control structure of the pneumatic biped Lucy. The robot is actuated with pleated pneumatic artificial muscles, which have interesting characteristics that can be exploited for legged machines. They have a high power to weight ratio, an adaptable compliance and they can reduce impact effects. The discussion of the control architecture focusses on the joint trajectory generator and the tracking controller which is divided in four parts: a computed torque module, an inverse delta-p unit, a local PI controller and a bang-bang pressure controller. The control design is divided into single support and double support where specifically the computed torque differs for these two phases. A full hybrid dynamic simulation model is used to evaluate the control architecture of the biped. This simulator combines the dynamical behaviour of the robot with the thermodynamical effects that take place in the muscle-valves system. The observed hardware limitations of the real robot and expected model errors are taken into account in order to give a realistic qualitative evaluation of the control performance and to test the robustness. Finally the first results of the incorporation of this control architecture in the real biped Lucy are given.
2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013
, with details of the nature of the infringement. We will investigate the claim and if justified,... more , with details of the nature of the infringement. We will investigate the claim and if justified, we will take the appropriate steps.
2014 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2014
High-performance actuators are required for numerous novel applications such as human-robot assis... more High-performance actuators are required for numerous novel applications such as human-robot assistive devices. The torque-to-weight ratio and energy efficiency of current actuation technology is often too low, which limits the performance of novel robots. Therefore, we developed a Series-Parallel Elastic Actuator (SPEA) which enables variable recruitment of parallel springs and variable load cancellation. Finding suitable intermittent mechanisms for the SPEA is however still challenging. This paper reports on the innovative design of an intermittent self-closing mechanism for a MACCEPA-based SPEA that can deliver bi-directional output torque and variable stiffness, while minimizing friction levels. Experiments on a one-layer intermittent self-closing mechanism are conducted to validate the working principle and the proposed model. A demonstrator of the MACCEPA-based SPEA with intermittent self-closing mechanism is presented and the experiments validate the modeled output torque and lowered motor torque for different stiffness settings.
2007 7th IEEE-RAS International Conference on Humanoid Robots, 2007
AbstractThe biped Lucy, powered by pleated pneumatic artificial muscles, has been built and cont... more AbstractThe biped Lucy, powered by pleated pneumatic artificial muscles, has been built and controlled and is able to walk up to a speed of 0.15m/s. The pressures inside the muscles are controlled by a joint trajectory tracking controller to track the desired joint trajectories ...
2009 IEEE International Conference on Rehabilitation Robotics, 2009
ABSTRACT This paper reports on the importance of understanding the human walking biomechanics for... more ABSTRACT 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 ankle-foot 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.
2008 2nd IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics, 2008
ABSTRACT Rehabilitation robotics is a young discipline that will become an imperative when the ag... more ABSTRACT Rehabilitation robotics is a young discipline that will become an imperative when the age of the population rises. The orthopaedic rehabilitation of the elbow joint poses some interesting challenges, discussed in this paper. There is a major difference between neuro-rehabilitation and orthopaedic rehabilitation and thus in the approaches necessary to tackle its challenges. Moreover, the elbow joint itself has some particular characteristics that render the rehabilitation process different from others. The mechanical design and design requirements of the developed powered elbow orthosis using MACCEPA actuators will be discussed, as well as the working principle of this novel rotational actuator with online adaptable compliance.
Proceedings of the 2005 IEEE International Conference on Robotics and Automation
Repetitive manual handling of heavy loads is common in assembly and is a frequent cause of lower ... more Repetitive manual handling of heavy loads is common in assembly and is a frequent cause of lower back disorders. This can have a significant impact on the quality of life and has a serious economic cost. This paper presents the concept of a lightweight manipulator that can interact directly with an operator in order to assist him in handling heavy loads. The advantages of the system, ergonomics, low weight, low cost, ease of operation and operator safety are a consequence of the use of Pleated Pneumatic Artificial Muscles as actuators. The design of a small-scale model of such a manipulator using these actuators is presented in detail. A simple position controller for the system is also presented.
2001 IEEE/ASME International Conference on Advanced Intelligent Mechatronics. Proceedings (Cat. No.01TH8556)
This contribution reports on a type of pneumatic artificial muscles (PAMs) that was recently deve... more This contribution reports on a type of pneumatic artificial muscles (PAMs) that was recently developed at the Vrije Universiteit Brussel, department of Mechanical Engineering. Its distinguishing feature is its pleated design. Due to this, it has a very high contraction force and an equally high travel. The weight of these pleated PAMs is very low: a muscle of only 60 gr can pull up to 3500 N and contract by an amount of 42%. Furthermore, dry friction and associated hysteresis, typical of many other designs, is avoided by the folding-unfolding action. This significantly simplifies position control using these actuators. Although the force-displacement characteristics of our actuators are non-linear, they can be effectively controlled using basic linear PI techniques. Another advantage of these actuators is their inherent and controllable compliance, making them ideally suited for walking/running machines or whenever delicate tasks, e.g. handling fragile objects, have to be performed. In view of all characteristics pleated PAMs are very well suited for automation and robotic applications.
ABSTRACT The purpose of this paper is to evaluate how healthy, neurologically intact humans adapt... more ABSTRACT The purpose of this paper is to evaluate how healthy, neurologically intact humans adapt their walking patterns to a powered compliant knee exoskeleton KNEXO that imply altered, less flexion gait pattern assistance during treadmill exercise. The experimental data of fifteen healthy subjects walked while wearing a pneumatically powered knee exoskeleton KNEXO on the treadmill was analyzed. We hypothesized that initially the gait kinematics of subject would be distorted by the added exoskeleton force. The muscle activity would be increased because of unusual gait pattern imposed by robot, but with practice knee torques became lower and also muscle activity decrease. Although KNEXO design includes safe compliance pneumatic actuators - Pleated Pneumatic Artificial Muscles (PPAM) we imply to obtain the Low Compliance (LC) and High Compliance (HC) behavior of the robot by adjusting the PID gains of the PSMC controller. In order to improve motor learning process the human-robot interaction (HRI) aspects of fifteen healthy subjects were observed and analyzed in different control setups of the robot.
Advances In Mobile Robotics - Proceedings of the Eleventh International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, 2008
This paper reports on the importance of understanding human walking biomechanics for the design o... more This paper reports on the importance of understanding human walking biomechanics for the design of new robotic and/or prosthetic feet. Based on human ankle behavior, the design specifications for new ankle-foot systems are determined. Three electrically powered ankle-foot design ...
Proceedings of the 28th Annual European Conference on Cognitive Ergonomics, 2010
ABSTRACT The past four years a unique robot platform 'Probo' is developed to study cogn... more ABSTRACT The past four years a unique robot platform 'Probo' is developed to study cognitive Human-Robot Interaction (HRI). The robot Probo (Saldien, 2009) is designed to act as a social interface, providing a natural interaction while employing human-like social cues and ...
2008 2nd IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics, 2008
ABSTRACT Robotic gait rehabilitation faces many challenges regarding ankle assistance, body weigh... more ABSTRACT Robotic gait rehabilitation faces many challenges regarding ankle assistance, body weight support and physical human-robot interaction. This paper reports on the development of a gait rehabilitation exoskeleton prototype intended as a platform for the evaluation of design and control concepts in view of improved physical human-robot interaction. The performance of proxy-based sliding mode control as a ldquorobot-in-chargerdquo control strategy is evaluated both in simulation and in experiments on a test setup. Compared to PID control, test results indicate good tracking performance and in particular safe system behavior.
2007 IEEE 10th International Conference on Rehabilitation Robotics, 2007
ABSTRACT This paper reports on the mechanical design of an active knee orthosis, powered by pleat... more ABSTRACT This paper reports on the mechanical design of an active knee orthosis, powered by pleated pneumatic artificial muscles. The orthosis is intended as a proof-of-concept rehabilitation device for the assessment of mechatronical design principles and testing of different control strategies. The general focus of this research is on the development of a step rehabilitation robot prototype consisting of a powered exoskeleton for the lower limbs.
This paper reports on the use of a new actuator, called Pleated Pneumatic Artificial Muscle, in a... more This paper reports on the use of a new actuator, called Pleated Pneumatic Artificial Muscle, in a one dimensional set-up, it is build as a footless leg with only the knee powered by a pair of Pleated Pneumatic Artificial Muscles. The main goal of this study is the evaluation of the adaptable passive behaviour of these Artificial Muscles in a leg, which can be exploited for an energy efficient way of walking for legged robots. The new actuator and its specific advantages for the use in legged robots will be discussed as well as the concept of the one dimensional set-up. It will be shown that a large amount of energy during a jump can be recuperated and continuous jumping can easily be achieved with low gauge pressures.
This paper intends to contribute to the study of dynamically balanced legged robots. A real-time ... more This paper intends to contribute to the study of dynamically balanced legged robots. A real-time applicable control algorithm for a planar one-legged robot is developed, which allows for locomotion on an irregular terrain. The simulated model consists of an articulated leg and a body, vertically placed upon the leg. During the stance phase the leg is supported by a massless foot. The algorithm is based on the choice of a number of objective locomotion parameters which can be changed from one hop to another. From a chosen initial configuration the robot is able to transfer to a chosen end configuration, while simultaneously controlling its forward velocity, its step length and its stepping height. The foot is thus being placed exactly on a chosen foothold. To reach this goal, the actuators track polynomial functions. The calculation of these functions is based on the objective parameters, and takes into account the constraints acting on the robot. These constraints result from the fa...
Automatic ball balancing is a technique adopted in rotordynamics to reduce unknown rotor unbalanc... more Automatic ball balancing is a technique adopted in rotordynamics to reduce unknown rotor unbalance automatically. This technique sounds appealing as it can ease a panoply of balancing issues considerably. The presence of stiction, however, scatters consistent qualitative balancing and led to a limited implementation in the industry. Temporary speed reduction, a recent technique, could be used as a countermeasure for the stiction-induced scattering. Presented in this paper is an in-depth study detailing how the technique should be implemented to guarantee effective balancing. By analysing a rotordynamic model of the Jeffcott kind, the influence of a multitude of parameters is studied such as the initial mass positions, the initial unbalance, the adopted speed profile, shaft damping, stiction and the speed reduction plateau of the adopted speed reduction strategy. The main findings of the study are that the adverse effects of stiction can be contained considerably using the speed redu...
Typical rotating machinery drive trains are prone to torsional vibrations. Especially those drive... more Typical rotating machinery drive trains are prone to torsional vibrations. Especially those drive trains that comprise one or more couplings which connect the multiple shafts. Since these vibrations rarely produce noise or vibration of the stationary frame, their presence is hardly noticeable. Moreover, unless an expensive torsional-related problem has become obvious, such drive trains are not instrumented with torsional vibration measurement equipment. Excessive levels can easily cause damage or even complete failure of the machine. So, when designing or retrofitting a machine, a comprehensive and detailed numerical torsional vibration analysis is crucial to avoid such problems. However, to accurately calculate the torsional modes, one has to account for the penetration effect of the shaft in the coupling hub, indicated by the shaft penetration factor, on the torsional stiffness calculation. Many guidelines and assumptions have been published for the stiffness calculation, however,...
Turbomachine rotors, supported by little damped rolling element bearings, are generally sensitive... more Turbomachine rotors, supported by little damped rolling element bearings, are generally sensitive to unbalance excitation. Accordingly, most machines incorporate squeeze film damper technology to dissipate mechanical energy caused by rotor vibrations and to ensure stable operation. When developing a novel geared turbomachine able to cover a large power range, a uniform mechanical drivetrain needs to perform well over the large operational loading range. Especially, the rotor support, containing a squeeze film damper and cylindrical roller bearing in series, is of vital importance in this respect. Thus, the direct objective of this research project was to map the performance of the envisioned rotor support by estimating the damping ratio based on the simulated and measured vibration response during run-up. An academic test rig was developed to provide an in-depth analysis on the key components in a more controlled setting. Both the numerical simulation and measurement results exposed...
2009 IEEE International Conference on Rehabilitation Robotics, 2009
Rehabilitation robotics is a young discipline that will become an imperative when the age of the ... more Rehabilitation robotics is a young discipline that will become an imperative when the age of the population will keep rising. The orthopaedic rehabilitation of the elbow joint poses some interesting challenges. The elbow joint itself has some particular characteristics that render the rehabilitation process different from others. The mechanical design of the developed powered elbow orthosis using MACCEPA actuators will be briefly discussed, as well as the mathematical model of the system.
Proceedings of the 2005 IEEE International Conference on Robotics and Automation
This paper reports on the control structure of the pneumatic biped Lucy. The robot is actuated wi... more This paper reports on the control structure of the pneumatic biped Lucy. The robot is actuated with pleated pneumatic artificial muscles, which have interesting characteristics that can be exploited for legged machines. They have a high power to weight ratio, an adaptable compliance and they can reduce impact effects. The discussion of the control architecture focusses on the joint trajectory generator and the tracking controller which is divided in four parts: a computed torque module, an inverse delta-p unit, a local PI controller and a bang-bang pressure controller. The control design is divided into single support and double support where specifically the computed torque differs for these two phases. A full hybrid dynamic simulation model is used to evaluate the control architecture of the biped. This simulator combines the dynamical behaviour of the robot with the thermodynamical effects that take place in the muscle-valves system. The observed hardware limitations of the real robot and expected model errors are taken into account in order to give a realistic qualitative evaluation of the control performance and to test the robustness. Finally the first results of the incorporation of this control architecture in the real biped Lucy are given.
2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013
, with details of the nature of the infringement. We will investigate the claim and if justified,... more , with details of the nature of the infringement. We will investigate the claim and if justified, we will take the appropriate steps.
2014 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2014
High-performance actuators are required for numerous novel applications such as human-robot assis... more High-performance actuators are required for numerous novel applications such as human-robot assistive devices. The torque-to-weight ratio and energy efficiency of current actuation technology is often too low, which limits the performance of novel robots. Therefore, we developed a Series-Parallel Elastic Actuator (SPEA) which enables variable recruitment of parallel springs and variable load cancellation. Finding suitable intermittent mechanisms for the SPEA is however still challenging. This paper reports on the innovative design of an intermittent self-closing mechanism for a MACCEPA-based SPEA that can deliver bi-directional output torque and variable stiffness, while minimizing friction levels. Experiments on a one-layer intermittent self-closing mechanism are conducted to validate the working principle and the proposed model. A demonstrator of the MACCEPA-based SPEA with intermittent self-closing mechanism is presented and the experiments validate the modeled output torque and lowered motor torque for different stiffness settings.
2007 7th IEEE-RAS International Conference on Humanoid Robots, 2007
AbstractThe biped Lucy, powered by pleated pneumatic artificial muscles, has been built and cont... more AbstractThe biped Lucy, powered by pleated pneumatic artificial muscles, has been built and controlled and is able to walk up to a speed of 0.15m/s. The pressures inside the muscles are controlled by a joint trajectory tracking controller to track the desired joint trajectories ...
2009 IEEE International Conference on Rehabilitation Robotics, 2009
ABSTRACT This paper reports on the importance of understanding the human walking biomechanics for... more ABSTRACT 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 ankle-foot 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.
2008 2nd IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics, 2008
ABSTRACT Rehabilitation robotics is a young discipline that will become an imperative when the ag... more ABSTRACT Rehabilitation robotics is a young discipline that will become an imperative when the age of the population rises. The orthopaedic rehabilitation of the elbow joint poses some interesting challenges, discussed in this paper. There is a major difference between neuro-rehabilitation and orthopaedic rehabilitation and thus in the approaches necessary to tackle its challenges. Moreover, the elbow joint itself has some particular characteristics that render the rehabilitation process different from others. The mechanical design and design requirements of the developed powered elbow orthosis using MACCEPA actuators will be discussed, as well as the working principle of this novel rotational actuator with online adaptable compliance.
Proceedings of the 2005 IEEE International Conference on Robotics and Automation
Repetitive manual handling of heavy loads is common in assembly and is a frequent cause of lower ... more Repetitive manual handling of heavy loads is common in assembly and is a frequent cause of lower back disorders. This can have a significant impact on the quality of life and has a serious economic cost. This paper presents the concept of a lightweight manipulator that can interact directly with an operator in order to assist him in handling heavy loads. The advantages of the system, ergonomics, low weight, low cost, ease of operation and operator safety are a consequence of the use of Pleated Pneumatic Artificial Muscles as actuators. The design of a small-scale model of such a manipulator using these actuators is presented in detail. A simple position controller for the system is also presented.
2001 IEEE/ASME International Conference on Advanced Intelligent Mechatronics. Proceedings (Cat. No.01TH8556)
This contribution reports on a type of pneumatic artificial muscles (PAMs) that was recently deve... more This contribution reports on a type of pneumatic artificial muscles (PAMs) that was recently developed at the Vrije Universiteit Brussel, department of Mechanical Engineering. Its distinguishing feature is its pleated design. Due to this, it has a very high contraction force and an equally high travel. The weight of these pleated PAMs is very low: a muscle of only 60 gr can pull up to 3500 N and contract by an amount of 42%. Furthermore, dry friction and associated hysteresis, typical of many other designs, is avoided by the folding-unfolding action. This significantly simplifies position control using these actuators. Although the force-displacement characteristics of our actuators are non-linear, they can be effectively controlled using basic linear PI techniques. Another advantage of these actuators is their inherent and controllable compliance, making them ideally suited for walking/running machines or whenever delicate tasks, e.g. handling fragile objects, have to be performed. In view of all characteristics pleated PAMs are very well suited for automation and robotic applications.
ABSTRACT The purpose of this paper is to evaluate how healthy, neurologically intact humans adapt... more ABSTRACT The purpose of this paper is to evaluate how healthy, neurologically intact humans adapt their walking patterns to a powered compliant knee exoskeleton KNEXO that imply altered, less flexion gait pattern assistance during treadmill exercise. The experimental data of fifteen healthy subjects walked while wearing a pneumatically powered knee exoskeleton KNEXO on the treadmill was analyzed. We hypothesized that initially the gait kinematics of subject would be distorted by the added exoskeleton force. The muscle activity would be increased because of unusual gait pattern imposed by robot, but with practice knee torques became lower and also muscle activity decrease. Although KNEXO design includes safe compliance pneumatic actuators - Pleated Pneumatic Artificial Muscles (PPAM) we imply to obtain the Low Compliance (LC) and High Compliance (HC) behavior of the robot by adjusting the PID gains of the PSMC controller. In order to improve motor learning process the human-robot interaction (HRI) aspects of fifteen healthy subjects were observed and analyzed in different control setups of the robot.
Advances In Mobile Robotics - Proceedings of the Eleventh International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, 2008
This paper reports on the importance of understanding human walking biomechanics for the design o... more This paper reports on the importance of understanding human walking biomechanics for the design of new robotic and/or prosthetic feet. Based on human ankle behavior, the design specifications for new ankle-foot systems are determined. Three electrically powered ankle-foot design ...
Proceedings of the 28th Annual European Conference on Cognitive Ergonomics, 2010
ABSTRACT The past four years a unique robot platform 'Probo' is developed to study cogn... more ABSTRACT The past four years a unique robot platform 'Probo' is developed to study cognitive Human-Robot Interaction (HRI). The robot Probo (Saldien, 2009) is designed to act as a social interface, providing a natural interaction while employing human-like social cues and ...
2008 2nd IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics, 2008
ABSTRACT Robotic gait rehabilitation faces many challenges regarding ankle assistance, body weigh... more ABSTRACT Robotic gait rehabilitation faces many challenges regarding ankle assistance, body weight support and physical human-robot interaction. This paper reports on the development of a gait rehabilitation exoskeleton prototype intended as a platform for the evaluation of design and control concepts in view of improved physical human-robot interaction. The performance of proxy-based sliding mode control as a ldquorobot-in-chargerdquo control strategy is evaluated both in simulation and in experiments on a test setup. Compared to PID control, test results indicate good tracking performance and in particular safe system behavior.
2007 IEEE 10th International Conference on Rehabilitation Robotics, 2007
ABSTRACT This paper reports on the mechanical design of an active knee orthosis, powered by pleat... more ABSTRACT This paper reports on the mechanical design of an active knee orthosis, powered by pleated pneumatic artificial muscles. The orthosis is intended as a proof-of-concept rehabilitation device for the assessment of mechatronical design principles and testing of different control strategies. The general focus of this research is on the development of a step rehabilitation robot prototype consisting of a powered exoskeleton for the lower limbs.
This paper reports on the use of a new actuator, called Pleated Pneumatic Artificial Muscle, in a... more This paper reports on the use of a new actuator, called Pleated Pneumatic Artificial Muscle, in a one dimensional set-up, it is build as a footless leg with only the knee powered by a pair of Pleated Pneumatic Artificial Muscles. The main goal of this study is the evaluation of the adaptable passive behaviour of these Artificial Muscles in a leg, which can be exploited for an energy efficient way of walking for legged robots. The new actuator and its specific advantages for the use in legged robots will be discussed as well as the concept of the one dimensional set-up. It will be shown that a large amount of energy during a jump can be recuperated and continuous jumping can easily be achieved with low gauge pressures.
This paper intends to contribute to the study of dynamically balanced legged robots. A real-time ... more This paper intends to contribute to the study of dynamically balanced legged robots. A real-time applicable control algorithm for a planar one-legged robot is developed, which allows for locomotion on an irregular terrain. The simulated model consists of an articulated leg and a body, vertically placed upon the leg. During the stance phase the leg is supported by a massless foot. The algorithm is based on the choice of a number of objective locomotion parameters which can be changed from one hop to another. From a chosen initial configuration the robot is able to transfer to a chosen end configuration, while simultaneously controlling its forward velocity, its step length and its stepping height. The foot is thus being placed exactly on a chosen foothold. To reach this goal, the actuators track polynomial functions. The calculation of these functions is based on the objective parameters, and takes into account the constraints acting on the robot. These constraints result from the fa...
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Papers by Dirk Lefeber