27 research outputs found
Modelling and analysis of dynamic frictional interactions of vibro-driven capsule systems with viscoelastic property
This paper studies the dynamic frictional interactions of the underactuated vibro-driven capsule systems with the viscoelastic property. Frictional dynamics of the capsule systems is an active research domain, while the online implementation and control of the friction models are still intractable tasks. This paper investigates the frictional characteristics of the capsule systems in the dynamic regime, including particularly the non-reversible drooping and hysteresis. Firstly, the frictional interaction dynamics is modelled and characterized using a combined physics-based and analytical-based approach. Subsequently, the qualitative changes in the capsule dynamics and friction-induced vibrational responses that triggered by multiple control parameters are discussed. It is found that the capsule dynamics is mainly periodic, and the motion velocity of the capsule systems can be controlled by appropriate tuning of the control parameters around the identified control points. Simulation results have a good agreement with the experimentally observed frictional characteristics. The effectiveness of the proposed method is verified in terms of satisfaction of the energy requirements and quenching of the friction-induced vibrations. It is also found that the frictional interaction dynamics of the capsule systems can be predicted for a wide range of vibrational behaviours. Finally, the importance of a concrete understanding and accurate description of the dynamic friction at the sliding substrate is highlighted
Bio-inspired robotic control in underactuation: principles for energy efficacy, dynamic compliance interactions and adaptability.
Biological systems achieve energy efficient and adaptive behaviours through extensive autologous and exogenous compliant interactions. Active dynamic compliances are created and enhanced from musculoskeletal system (joint-space) to external environment (task-space) amongst the underactuated motions. Underactuated systems with viscoelastic property are similar to these biological systems, in that their self-organisation and overall tasks must be achieved by coordinating the subsystems and dynamically interacting with the environment. One important question to raise is: How can we design control systems to achieve efficient locomotion, while adapt to dynamic conditions as the living systems do? In this thesis, a trajectory planning algorithm is developed for underactuated microrobotic systems with bio-inspired self-propulsion and viscoelastic property to achieve synchronized motion in an energy efficient, adaptive and analysable manner. The geometry of the state space of the systems is explicitly utilized, such that a synchronization of the generalized coordinates is achieved in terms of geometric relations along the desired motion trajectory. As a result, the internal dynamics complexity is sufficiently reduced, the dynamic couplings are explicitly characterised, and then the underactuated dynamics are projected onto a hyper-manifold. Following such a reduction and characterization, we arrive at mappings of system compliance and integrable second-order dynamics with the passive degrees of freedom. As such, the issue of trajectory planning is converted into convenient nonlinear geometric analysis and optimal trajectory parameterization. Solutions of the reduced dynamics and the geometric relations can be obtained through an optimal motion trajectory generator. Theoretical background of the proposed approach is presented with rigorous analysis and developed in detail for a particular example. Experimental studies are conducted to verify the effectiveness of the proposed method. Towards compliance interactions with the environment, accurate modelling or prediction of nonlinear friction forces is a nontrivial whilst challenging task. Frictional instabilities are typically required to be eliminated or compensated through efficiently designed controllers. In this work, a prediction and analysis framework is designed for the self-propelled vibro-driven system, whose locomotion greatly relies on the dynamic interactions with the nonlinear frictions. This thesis proposes a combined physics-based and analytical-based approach, in a manner that non-reversible characteristic for static friction, presliding as well as pure sliding regimes are revealed, and the frictional limit boundaries are identified. Nonlinear dynamic analysis and simulation results demonstrate good captions of experimentally observed frictional characteristics, quenching of friction-induced vibrations and satisfaction of energy requirements. The thesis also performs elaborative studies on trajectory tracking. Control schemes are designed and extended for a class of underactuated systems with concrete considerations on uncertainties and disturbances. They include a collocated partial feedback control scheme, and an adaptive variable structure control scheme with an elaborately designed auxiliary control variable. Generically, adaptive control schemes using neural networks are designed to ensure trajectory tracking. Theoretical background of these methods is presented with rigorous analysis and developed in detail for particular examples. The schemes promote the utilization of linear filters in the control input to improve the system robustness. Asymptotic stability and convergence of time-varying reference trajectories for the system dynamics are shown by means of Lyapunov synthesis
Energy-Efficient Design and Control of a Vibro-Driven Robot
Vibro-driven robotic (VDR) systems use stick-slip motions for locomotion. Due to the underactuated nature of the system, efficient design and control are still open problems. We present a new energy preserving design based on a spring-augmented pendulum. We indirectly control the friction-induced stick-slip motions by exploiting the passive dynamics in order to achieve an improvement in overall travelling distance and energy efficacy. Both collocated and non-collocated constraint conditions are elaborately analysed and considered to obtain a desired trajectory generation profile. For tracking control, we develop a partial feedback controller which for the pendulum which counteracts the dynamic contributions from the platform. Comparative simulation studies show the effectiveness and intriguing performance of the proposed approach, while its feasibility is experimentally verified through a physical robot. Our robot is to the best of our knowledge the first nonlinear-motion prototype in literature towards the VDR systems
Π‘ΠΈΠ½ΡΠ΅Π· ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½ΠΎΠ³ΠΎ Π΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠ΅ΠΆΠΈΠΌΠ° Π΄Π²ΠΈΠΆΠ΅Π½ΠΈΡ ΡΡΡΠ΅Π»Ρ ΠΌΠ°Π½ΠΈΠΏΡΠ»ΡΡΠΎΡΠ°, ΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½Π½ΠΎΠ³ΠΎ Π½Π° ΡΠΏΡΡΠ³ΠΎΠΌ ΠΎΡΠ½ΠΎΠ²Π°Π½ΠΈΠΈ
In order to increase reliability and accuracy of robot manipulators or other construction equipment used for lifting operations an optimum dynamic mode for moving its boom system has been calculated in the paper. Results of the research have made it possible to construct a mathematical model for manipulator movement and obtain kinematic characteristics of the optimum dynamic mode. While determining the optimum dynamic motion mode, a criterion action has been used as an optimization criterion which represents a time integral with an integrand function expressing a dynamic component of manipulator drive power. Functions for changing kinematic characteristics of an manipulator boom have been calculated when it moves from one predetermined position to another one and which correspond to optimum dynamic mode of motion. Search for an optimum motion mode has been performed by minimizing the optimization criterion using the EulerβPoisson equations. In this case a generalized angle of rotation has been used which permits to relate movement of the boom and oscillations of its support part. As a linking component differential equations of system motion have been also applied, in which relationships between an oscillation angle, rigidity of a manipulator support, and its mass-geometric characteristics have been recorded. Results of the work can be useful for refinement and improvement of existing engineering methods for calculating the drive mechanisms of manipulators both at design/construction stages and in real operation modes, and the results can also be used while making design or improvement of similar executive mechanisms for construction equipment and robots.Π‘ ΡΠ΅Π»ΡΡ ΠΏΠΎΠ²ΡΡΠ΅Π½ΠΈΡ Π½Π°Π΄Π΅ΠΆΠ½ΠΎΡΡΠΈ ΠΈ ΡΠΎΡΠ½ΠΎΡΡΠΈ Π²ΡΠΏΠΎΠ»Π½Π΅Π½ΠΈΡ ΠΌΠ°Π½ΠΈΠΏΡΠ»ΡΡΠΎΡΠ°ΠΌΠΈ-ΡΠΎΠ±ΠΎΡΠ°ΠΌΠΈ Π»ΠΈΠ±ΠΎ ΠΈΠ½ΠΎΠΉ ΡΡΡΠΎΠΈΡΠ΅Π»ΡΠ½ΠΎΠΉ ΡΠ΅Ρ
Π½ΠΈΠΊΠΎΠΉ Π³ΡΡΠ·ΠΎΠΏΠΎΠ΄ΡΠ΅ΠΌΠ½ΡΡ
ΠΎΠΏΠ΅ΡΠ°ΡΠΈΠΉ ΡΠ°ΡΡΡΠΈΡΠ°Π½ ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½ΡΠΉ Π΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΈΠΉ ΡΠ΅ΠΆΠΈΠΌ ΠΏΠ΅ΡΠ΅ΠΌΠ΅ΡΠ΅Π½ΠΈΡ ΠΈΡ
ΡΡΡΠ΅Π»ΠΎΠ²ΠΎΠΉ ΡΠΈΡΡΠ΅ΠΌΡ. Π ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠ΅ ΠΏΡΠΎΠ²Π΅Π΄Π΅Π½Π½ΡΡ
ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠΉ ΠΏΠΎΡΡΡΠΎΠ΅Π½Π° ΠΌΠ°ΡΠ΅ΠΌΠ°ΡΠΈΡΠ΅ΡΠΊΠ°Ρ ΠΌΠΎΠ΄Π΅Π»Ρ Π΄Π²ΠΈΠΆΠ΅Π½ΠΈΡ ΠΌΠ°Π½ΠΈΠΏΡΠ»ΡΡΠΎΡΠ° ΠΈ ΠΏΠΎΠ»ΡΡΠ΅Π½Ρ ΠΊΠΈΠ½Π΅ΠΌΠ°ΡΠΈΡΠ΅ΡΠΊΠΈΠ΅ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊΠΈ ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½ΠΎΠ³ΠΎ Π΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠ΅ΠΆΠΈΠΌΠ°. ΠΡΠΈ ΠΎΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΠΈ ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½ΠΎΠ³ΠΎ Π΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠ΅ΠΆΠΈΠΌΠ° Π΄Π²ΠΈΠΆΠ΅Π½ΠΈΡ Π² ΠΊΠ°ΡΠ΅ΡΡΠ²Π΅ ΠΎΠΏΡΠΈΠΌΠΈΠ·Π°ΡΠΈΠΎΠ½Π½ΠΎΠ³ΠΎ ΠΊΡΠΈΡΠ΅ΡΠΈΡ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΎ ΠΊΡΠΈΡΠ΅ΡΠΈΠ°Π»ΡΠ½ΠΎΠ΅ Π΄Π΅ΠΉΡΡΠ²ΠΈΠ΅, ΠΏΡΠ΅Π΄ΡΡΠ°Π²Π»ΡΡΡΠ΅Π΅ ΡΠΎΠ±ΠΎΠΉ ΠΈΠ½ΡΠ΅Π³ΡΠ°Π» ΠΏΠΎ Π²ΡΠ΅ΠΌΠ΅Π½ΠΈ Ρ ΠΏΠΎΠ΄ΡΠ½ΡΠ΅Π³ΡΠ°Π»ΡΠ½ΠΎΠΉ ΡΡΠ½ΠΊΡΠΈΠ΅ΠΉ, Π²ΡΡΠ°ΠΆΠ°ΡΡΠ΅ΠΉ Π΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΡΡ ΡΠΎΡΡΠ°Π²Π»ΡΡΡΡΡ ΠΌΠΎΡΠ½ΠΎΡΡΠΈ ΠΏΡΠΈΠ²ΠΎΠ΄Π° ΠΌΠ°Π½ΠΈΠΏΡΠ»ΡΡΠΎΡΠ°. Π Π°ΡΡΡΠΈΡΠ°Π½Ρ ΡΡΠ½ΠΊΡΠΈΠΈ ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΡ ΠΊΠΈΠ½Π΅ΠΌΠ°ΡΠΈΡΠ΅ΡΠΊΠΈΡ
Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊ ΡΡΡΠ΅Π»Ρ ΠΌΠ°Π½ΠΈΠΏΡΠ»ΡΡΠΎΡΠ° ΠΏΡΠΈ Π΅Π΅ Π΄Π²ΠΈΠΆΠ΅Π½ΠΈΠΈ ΠΈΠ· ΠΎΠ΄Π½ΠΎΠ³ΠΎ Π·Π°Π΄Π°Π½Π½ΠΎΠ³ΠΎ ΠΏΠΎΠ»ΠΎΠΆΠ΅Π½ΠΈΡ Π² Π΄ΡΡΠ³ΠΎΠ΅, ΠΊΠΎΡΠΎΡΡΠ΅ ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΡΡΡ ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½ΠΎΠΌΡ Π΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΎΠΌΡ ΡΠ΅ΠΆΠΈΠΌΡ Π΄Π²ΠΈΠΆΠ΅Π½ΠΈΡ. ΠΠΎΠΈΡΠΊ ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½ΠΎΠ³ΠΎ ΡΠ΅ΠΆΠΈΠΌΠ° Π΄Π²ΠΈΠΆΠ΅Π½ΠΈΡ Π²ΡΠΏΠΎΠ»Π½Π΅Π½ ΠΏΠΎΡΡΠ΅Π΄ΡΡΠ²ΠΎΠΌ ΠΌΠΈΠ½ΠΈΠΌΠΈΠ·Π°ΡΠΈΠΈ ΠΊΡΠΈΡΠ΅ΡΠΈΡ ΠΎΠΏΡΠΈΠΌΠΈΠ·Π°ΡΠΈΠΈ ΠΏΡΠΈ ΠΏΠΎΠΌΠΎΡΠΈ ΡΡΠ°Π²Π½Π΅Π½ΠΈΠΉ ΠΠΉΠ»Π΅ΡΠ° β ΠΡΠ°ΡΡΠΎΠ½Π°. ΠΡΠΈ ΡΡΠΎΠΌ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ ΠΎΠ±ΠΎΠ±ΡΠ΅Π½Π½ΡΠΉ ΡΠ³ΠΎΠ» ΠΏΠΎΠ²ΠΎΡΠΎΡΠ°, ΠΊΠΎΡΠΎΡΡΠΉ ΠΏΠΎΠ·Π²ΠΎΠ»ΠΈΠ» ΡΠ²ΡΠ·Π°ΡΡ ΠΏΠ΅ΡΠ΅ΠΌΠ΅ΡΠ΅Π½ΠΈΠ΅ ΡΡΡΠ΅Π»Ρ ΠΈ ΠΊΠΎΠ»Π΅Π±Π°Π½ΠΈΡ Π΅Π΅ ΠΎΠΏΠΎΡΠ½ΠΎΠΉ ΡΠ°ΡΡΠΈ. Π ΠΊΠ°ΡΠ΅ΡΡΠ²Π΅ ΡΠ²ΡΠ·ΡΡΡΠ΅Π³ΠΎ ΠΊΠΎΠΌΠΏΠΎΠ½Π΅Π½ΡΠ° ΡΠ°ΠΊΠΆΠ΅ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½Ρ Π΄ΠΈΡΡΠ΅ΡΠ΅Π½ΡΠΈΠ°Π»ΡΠ½ΡΠ΅ ΡΡΠ°Π²Π½Π΅Π½ΠΈΡ Π΄Π²ΠΈΠΆΠ΅Π½ΠΈΡ ΡΠΈΡΡΠ΅ΠΌΡ, Π³Π΄Π΅ Π·Π°ΠΏΠΈΡΠ°Π½Ρ Π²Π·Π°ΠΈΠΌΠΎΡΠ²ΡΠ·ΠΈ ΠΌΠ΅ΠΆΠ΄Ρ ΡΠ³Π»ΠΎΠΌ ΠΊΠΎΠ»Π΅Π±Π°Π½ΠΈΡ, ΠΆΠ΅ΡΡΠΊΠΎΡΡΡΡ ΠΎΠΏΠΎΡΡ ΠΌΠ°Π½ΠΈΠΏΡΠ»ΡΡΠΎΡΠ° ΠΈ Π΅Π³ΠΎ ΠΌΠ°ΡΡΠΎΠ²ΠΎ-Π³Π΅ΠΎΠΌΠ΅ΡΡΠΈΡΠ΅ΡΠΊΠΈΠΌΠΈ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊΠ°ΠΌΠΈ. Π Π΅Π·ΡΠ»ΡΡΠ°ΡΡ ΡΠ°Π±ΠΎΡΡ ΠΌΠΎΠ³ΡΡ Π±ΡΡΡ ΠΏΠΎΠ»Π΅Π·Π½Ρ Π΄Π»Ρ ΡΡΠΎΡΠ½Π΅Π½ΠΈΡ ΠΈ ΡΡΠΎΠ²Π΅ΡΡΠ΅Π½ΡΡΠ²ΠΎΠ²Π°Π½ΠΈΡ ΡΡΡΠ΅ΡΡΠ²ΡΡΡΠΈΡ
ΠΈΠ½ΠΆΠ΅Π½Π΅ΡΠ½ΡΡ
ΠΌΠ΅ΡΠΎΠ΄ΠΎΠ² ΡΠ°ΡΡΠ΅ΡΠ° ΠΏΡΠΈΠ²ΠΎΠ΄Π½ΡΡ
ΠΌΠ΅Ρ
Π°Π½ΠΈΠ·ΠΌΠΎΠ² ΠΌΠ°Π½ΠΈΠΏΡΠ»ΡΡΠΎΡΠΎΠ² ΠΊΠ°ΠΊ Π½Π° ΡΡΠ°Π΄ΠΈΡΡ
ΠΏΡΠΎΠ΅ΠΊΡΠΈΡΠΎΠ²Π°Π½ΠΈΡ/ΠΊΠΎΠ½ΡΡΡΡΠΈΡΠΎΠ²Π°Π½ΠΈΡ, ΡΠ°ΠΊ ΠΈ Π² ΡΠ΅ΠΆΠΈΠΌΠ°Ρ
ΡΠ΅Π°Π»ΡΠ½ΠΎΠΉ ΡΠΊΡΠΏΠ»ΡΠ°ΡΠ°ΡΠΈΠΈ, Π° ΡΠ°ΠΊΠΆΠ΅ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°ΡΡΡΡ ΠΏΡΠΈ ΠΏΡΠΎΠ΅ΠΊΡΠΈΡΠΎΠ²Π°Π½ΠΈΠΈ ΠΈΠ»ΠΈ ΡΡΠΎΠ²Π΅ΡΡΠ΅Π½ΡΡΠ²ΠΎΠ²Π°Π½ΠΈΠΈ ΠΏΠΎΠ΄ΠΎΠ±Π½ΡΡ
ΠΈΡΠΏΠΎΠ»Π½ΠΈΡΠ΅Π»ΡΠ½ΡΡ
ΠΌΠ΅Ρ
Π°Π½ΠΈΠ·ΠΌΠΎΠ² ΡΡΡΠΎΠΈΡΠ΅Π»ΡΠ½ΠΎΠΉ ΡΠ΅Ρ
Π½ΠΈΠΊΠΈ ΠΈ ΡΠΎΠ±ΠΎΡΠΎΠ²
On the development of a cybernetic prosthetic hand
The human hand is the end organ of the upper limb, which in humans serves the important
function of prehension, as well as being an important organ for sensation and communication.
It is a marvellous example of how a complex mechanism can be implemented,
capable of realizing very complex and useful tasks using a very effective combination of
mechanisms, sensing, actuation and control functions.
In this thesis, the road towards the realization of a cybernetic hand has been presented.
After a detailed analysis of the model, the human hand, a deep review of the state of the
art of artificial hands has been carried out. In particular, the performance of prosthetic
hands used in clinical practice has been compared with the research prototypes, both for
prosthetic and for robotic applications. By following a biomechatronic approach, i.e. by
comparing the characteristics of these hands with the natural model, the human hand, the
limitations of current artificial devices will be put in evidence, thus outlining the design
goals for a new cybernetic device.
Three hand prototypes with a high number of degrees of freedom have been realized and
tested: the first one uses microactuators embedded inside the structure of the fingers, and
the second and third prototypes exploit the concept of microactuation in order to increase
the dexterity of the hand while maintaining the simplicity for the control. In particular, a
framework for the definition and realization of the closed-loop electromyographic control of
these devices has been presented and implemented.
The results were quite promising, putting in evidence that, in the future, there could
be two different approaches for the realization of artificial devices. On one side there
could be the EMG-controlled hands, with compliant fingers but only one active degree of
freedom. On the other side, more performing artificial hands could be directly interfaced
with the peripheral nervous system, thus establishing a bi-directional communication with
the human brain
Recommended from our members
Bio-inspired robotic joint and manipulator : from biomechanical experimentation and modeling to human-like compliant finger design and control
textOne of the greatest challenges in controlling robotic hands is grasping and manipulating objects in unstructured and uncertain environments. Robotic hands are typically too rigid to react against unexpected impacts and disturbances in order to prevent damage. The human hands have great versatility and robustness due, in part, to the passive compliance and damping. Designing mechanical elements that are inspired by the nonlinear joint compliance of human hands is a promising solution to achieve human-like grasping and manipulation. However, the exact role of biomechanical elements in realizing joint stiffness is unknown. We conducted a series of experiments to investigate nonlinear stiffness and damping of the metacarpophalangeal (MCP) joint at the index finger. We designed a custom-made mechanism to integrate electromyography sensors (EMGs) and a motion capture system to collect data from 19 subjects. We investigated the relative contributions of muscle-tendon units and the MCP capsule ligament complex to joint stiffness with subject-specific modeling. The results show that the muscle-tendon units provide limited contribution to the passive joint compliance. This findings indicate that the parallel compliance, in the form of the capsule-ligament complex, is significant in defining the passive properties of the hand. To identify the passive damping, we used the hysteresis loops to investigate the energy dissipation function. We used symbolic regression and principal component analysis to derive and interpret the damping models. The results show that the nonlinear viscous damping depends on the cyclic frequency, and fluid and structural types of damping also exist at the MCP joint. Inspired by the nonlinear stiffness of the MCP joint, we developed a miniaturized mechanism that uses pouring liquid plastic to design energy storing elements. The key innovations in this design are: a) a set of nonlinear elasticity of compliant materials, b) variable pulley configurations to tune the stiffness profile, and c) pretension mechanism to scale the stiffness profile. The design exhibits human-like passive compliance. By taking advantage of miniaturized joint size and additive manufacturing, we incorporated the novel joint design in a novel robotic manipulator with six series elastic actuators (SEA). The robotic manipulator has passive joint compliance with the intrinsic property of human hands. To validate the system, we investigated the Cartesian stiffness of grasping with low-level force control. The results show that that the overall system performs a great force tracking with position feedback. The parallel compliance decreases the motor efforts and can stabilize the system.Mechanical Engineerin
Soft Robotics: Design for Simplicity, Performance, and Robustness of Robots for Interaction with Humans.
This thesis deals with the design possibilities concerning the next generation of advanced Robots. Aim of the work is to study, analyse and realise artificial systems that are essentially simple, performing and robust and can live and coexist with humans. The main design guideline followed in doing so is the Soft Robotics Approach, that implies the design of systems with intrinsic mechanical compliance in their architecture. The first part of the thesis addresses design of new soft robotics actuators, or robotic muscles. At the beginning are provided information about what a robotic muscle is and what is needed to realise it. A possible classification of these systems is analysed and some criteria useful for their comparison are explained. After, a set of functional specifications and parameters is identified and defined, to characterise a specific subset of this kind of actuators, called Variable Stiffness Actuators. The selected parameters converge in a data-sheet that easily defines performance and abilities of the robotic system. A complete strategy for the design and realisation of this kind of system is provided, which takes into account their me- chanical morphology and architecture. As consequence of this, some new actuators are developed, validated and employed in the execution of complex experimental tasks. In particular the actuator VSA-Cube and its add-on, a Variable Damper, are developed as the main com- ponents of a robotics low-cost platform, called VSA-CubeBot, that
v
can be used as an exploratory platform for multi degrees of freedom experiments. Experimental validations and mathematical models of the system employed in multi degrees of freedom tasks (bimanual as- sembly and drawing on an uneven surface), are reported.
The second part of the thesis is about the design of multi fingered hands for robots. In this part of the work the Pisa-IIT SoftHand is introduced. It is a novel robot hand prototype designed with the purpose of being as easily usable, robust and simple as an industrial gripper, while exhibiting a level of grasping versatility and an aspect comparable to that of the human hand. In the thesis the main theo- retical tool used to enable such simplification, i.e. the neuroscienceβ based notion of soft synergies, are briefly reviewed. The approach proposed rests on ideas coming from underactuated hand design. A synthesis method to realize a desired set of soft synergies through the principled design of adaptive underactuated mechanisms, which is called the method of adaptive synergies, is discussed. This ap- proach leads to the design of hands accommodating in principle an arbitrary number of soft synergies, as demonstrated in grasping and manipulation simulations and experiments with a prototype. As a particular instance of application of the method of adaptive syner- gies, the PisaβIIT SoftHand is then described in detail. The design and implementation of the prototype hand are shown and its effec- tiveness demonstrated through grasping experiments. Finally, control of the Pisa/IIT Hand is considered. Few different control strategies are adopted, including an experimental setup with the use of surface Electromyographic signals
Development and Biomechanical Analysis toward a Mechanically Passive Wearable Shoulder Exoskeleton
Shoulder disability is a prevalent health issue associated with various orthopedic and neurological conditions, like rotator cuff tear and peripheral nerve injury. Many individuals with shoulder disability experience mild to moderate impairment and struggle with elevating the shoulder or holding the arm against gravity. To address this clinical need, I have focused my research on developing wearable passive exoskeletons that provide continuous at-home movement assistance. Through a combination of experiments and computational tools, I aim to optimize the design of these exoskeletons.
In pursuit of this goal, I have designed, fabricated, and preliminarily evaluated a wearable, passive, cam-driven shoulder exoskeleton prototype. Notably, the exoskeleton features a modular spring-cam-wheel module, allowing customizable assistive force to compensate for different proportions of the shoulder elevation moment due to gravity. The results of my research demonstrated that this exoskeleton, providing modest one-fourth gravity moment compensation at the shoulder, can effectively reduce muscle activity, including deltoid and rotator cuff muscles.
One crucial aspect of passive shoulder exoskeleton design is determining the optimal anti-gravity assistance level. I have addressed this challenge using computational tools and found that an assistance level within the range of 20-30% of the maximum gravity torque at the shoulder joint yields superior performance for specific shoulder functional tasks.
When facing a new task dynamic, such as wearing a passive shoulder exoskeleton, the human neuro-musculoskeletal system adapts and modulates limb impedance at the end-limb (i.e., hand) to enhance task stability. I have presented development and validation of a realistic neuromusculoskeletal model of the upper limb that can predict stiffness modulation and motor adaptation in response to newly introduced environments and force fields. Future studies will explore the model\u27s applicability in predicting stiffness modulation for 3D movements in novel environments, such as passive assistive devices\u27 force fields