Norbert S´ark´any
(Supervisors: Dr. Gy¨orgy Cserey, Dr. P´eter Szolgay) sarkany.norbert@itk.ppke.hu
Abstract—This paper presents a design of an anthropomorphic biomimetic test bed hand, focusing on the design of the fingers and its bio-inspired flexor-extensor like control. The kinematic description, the detailed explanation and presentation of the 3D CAD design are included. The description of the applied 3D touch and magnetic sensors are also detailed in the article. Functional simulation results and also the first experiments of the hardware prototype gave promising results and show that the approach can be an effective solution for the need of a hand test bed.
Keywords-robotics; bionics; biomimetic; test bed; robotic hand I. INTRODUCTION
In the last twenty years there was an extensive research about robotic hands, their goal was to design and develop an anthropomorphic dexterous hand [1], [2], [3], [4], [5], [6].
There are two designs, one with a local control where the actuators are in the hand [1], [3], [4], its reduces the amount of space which it requires, and the weight. The reduced weight is always an important aspect but in many cases this reduces the DOF. The second design is where the actuated structure and the actuator mechanism are separated and connected with artificial tendons, such a hand is capable to do manipulation tasks like a human hand can do, here every joint has an independent control, and there are no passively controlled joints. The commercially available prosthetics are similar to the first type but are limited in their movement capability and they have a lack of sensory information and less of control. In this paper a design of an anthropomorphic biomimetic hand test bed is discussed. Primarily the design of the finger and the concept of the actuation system is shown. The main goal of the research is to have a fully functional biomimetic hand test bed. Which can be used in robotic applications, research and it also give a basis of new prosthetics design too.
In Section. II the anatomical bases are presented, Section III shows the control and sensing structures in the human nevus system. Section IV discuss the finger kinematics and represen-tation. Section V shows the biomimetic test bed setup for one finger, Section VI shows the concept of control and sensig in a finger. Finally, conclusions and future work are discussed in Section. VII.
II. ANATOMICALBASES
A finger is a limb of our body a tool of manipulation and sensing, it is found in the hand. Normally a human has five of them Thumb, Index, Middle, Ring and Little finger. The Thumb is structurally a little different from the other five, it has two phalanges and the other four have three. The components
which constitute the fingers are the muscle, the ligaments, and the articulations. These mechanical structures make it possible to have 24 DOF and to achieve a smooth, compliant and accurate movement.
(a) (b) (c)
Fig. 1: General articulations structure (Fig. 1a), finger and its articulations(Fig. 1b , Fig. 1c)
A. Articulations
In our skeletal structure bones can connect in two ways, con-tinues and interrupted. The concon-tinues connections (synarthro-sis) also can be divided in to two groups transient and perma-nent. The first one is by evolving bones and the other at the bone connections. The interrupted connections are the joints (articulations) (Fig. 1). There is a more or less gap between the connecting bone parts. We talk about simple articulations when two bones meet. The components in the articulation can be permanent or collateral. In the simple articulations from the two bone parts one has a globular articulation head and the other has a concave score. The head of the articulation is not always globular, it can be cylindrical, elliptical. The shape of the articulation head is important because it determines the extent and quality of movement.
Figure 1 shows the structure and the parts of the articula-tions. In the articulation are the two connecting bone parts with articulation cartilage at the end, in the small gepp between the bones is the synovial fluid. The bones are actually held together by the articulation socket and fibers. The articulation system decided here is similar in all kind of articulation types in the hand. These articulation types are saddle joint, cylinder joint and ball joint.
B. Actuation anatomical components
The most common forces transmission agent in the human body is the tendon. The dense connective tissue is the most
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[4] Pan, Y., et al., Neurotactin, a membrane-anchored chemokine upregulated in brain inflammation. Nature, 1997. 387(6633): p. 611-7.
[5] Shah, R., et al., Fractalkine is a novel human adipochemokine associated with type 2 diabetes. Diabetes, 2011. 60(5): p. 1512-8.
[6] Wolf, Y., et al., Microglia, seen from the CX3CR1 angle. Front Cell Neurosci, 2013. 7: p. 26.
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[8] Morris, D.L., et al., CX3CR1 deficiency does not influence trafficking of adipose tissue macrophages in mice with diet-induced obesity. Obesity (Silver Spring), 2012. 20(6): p. 1189-99.
Biomimetic Test bed Hand
Norbert S´ark´any
(Supervisors: Dr. Gy¨orgy Cserey, Dr. P´eter Szolgay) sarkany.norbert@itk.ppke.hu
Abstract—This paper presents a design of an anthropomorphic biomimetic test bed hand, focusing on the design of the fingers and its bio-inspired flexor-extensor like control. The kinematic description, the detailed explanation and presentation of the 3D CAD design are included. The description of the applied 3D touch and magnetic sensors are also detailed in the article. Functional simulation results and also the first experiments of the hardware prototype gave promising results and show that the approach can be an effective solution for the need of a hand test bed.
Keywords-robotics; bionics; biomimetic; test bed; robotic hand I. INTRODUCTION
In the last twenty years there was an extensive research about robotic hands, their goal was to design and develop an anthropomorphic dexterous hand [1], [2], [3], [4], [5], [6].
There are two designs, one with a local control where the actuators are in the hand [1], [3], [4], its reduces the amount of space which it requires, and the weight. The reduced weight is always an important aspect but in many cases this reduces the DOF. The second design is where the actuated structure and the actuator mechanism are separated and connected with artificial tendons, such a hand is capable to do manipulation tasks like a human hand can do, here every joint has an independent control, and there are no passively controlled joints. The commercially available prosthetics are similar to the first type but are limited in their movement capability and they have a lack of sensory information and less of control. In this paper a design of an anthropomorphic biomimetic hand test bed is discussed. Primarily the design of the finger and the concept of the actuation system is shown. The main goal of the research is to have a fully functional biomimetic hand test bed. Which can be used in robotic applications, research and it also give a basis of new prosthetics design too.
In Section. II the anatomical bases are presented, Section III shows the control and sensing structures in the human nevus system. Section IV discuss the finger kinematics and represen-tation. Section V shows the biomimetic test bed setup for one finger, Section VI shows the concept of control and sensig in a finger. Finally, conclusions and future work are discussed in Section. VII.
II. ANATOMICALBASES
A finger is a limb of our body a tool of manipulation and sensing, it is found in the hand. Normally a human has five of them Thumb, Index, Middle, Ring and Little finger. The Thumb is structurally a little different from the other five, it has two phalanges and the other four have three. The components
which constitute the fingers are the muscle, the ligaments, and the articulations. These mechanical structures make it possible to have 24 DOF and to achieve a smooth, compliant and accurate movement.
(a) (b) (c)
Fig. 1: General articulations structure (Fig. 1a), finger and its articulations(Fig. 1b , Fig. 1c)
A. Articulations
In our skeletal structure bones can connect in two ways, con-tinues and interrupted. The concon-tinues connections (synarthro-sis) also can be divided in to two groups transient and perma-nent. The first one is by evolving bones and the other at the bone connections. The interrupted connections are the joints (articulations) (Fig. 1). There is a more or less gap between the connecting bone parts. We talk about simple articulations when two bones meet. The components in the articulation can be permanent or collateral. In the simple articulations from the two bone parts one has a globular articulation head and the other has a concave score. The head of the articulation is not always globular, it can be cylindrical, elliptical. The shape of the articulation head is important because it determines the extent and quality of movement.
Figure 1 shows the structure and the parts of the articula-tions. In the articulation are the two connecting bone parts with articulation cartilage at the end, in the small gepp between the bones is the synovial fluid. The bones are actually held together by the articulation socket and fibers. The articulation system decided here is similar in all kind of articulation types in the hand. These articulation types are saddle joint, cylinder joint and ball joint.
B. Actuation anatomical components
The most common forces transmission agent in the human body is the tendon. The dense connective tissue is the most N. Sárkány, “Biomimetic test bed hand,”
in Proceedings of the Interdisciplinary Doctoral School in the 2012-2013 Academic Year, T. Roska, G. Prószéky, P. Szolgay, Eds.
Faculty of Information Technology, Pázmány Péter Catholic University.
Budapest, Hungary: Pázmány University ePress, 2013, vol. 8, pp. 63-66.
(a) (b) (c)
Fig. 2: Human finger tendons articulations (Fig. 2a), Extensor-Flexor mechanism (Fig. 2b), Human hand muscle and tendon structure (Fig. 2c)
arranged form of connective tissues typical occurrence are tendons. Tendons are like strong braided ropes, they contains a lots of small fibers bundled to geather.
Muscles tissues are the source of force in the body due to this are we capable to move our limbs. There are three main type of muscle in the body: skeletal, smooth, cardiac. The process of movement in the hand has two parts an extensor and a flexor muscle. This way our body can move smooth and gently. Almost all degrees of freedom have its extensor flexor component.
III. CONTROL AND SENSING
The Central Nervous System (CNS) contains the spinal cord and several part of the brain. For the involuntary control of our body the main center is our spinal cord from skull down.
A. Somatic and autonomic motoric system
There are two types of control of our muscles a reflex action and a voluntary. The reflexes are not conscious they emerge from a low level of control from the spinal cord. These low level controls can be divided in two groups based on their source: muscle origin or external (skin) origin reflex.
Fig. 3: Patela reflex
1) Proprioceptive (Myotacticus) reflex: The meaning of muscle origin reflex is that the reflex source is in the skeletal muscle, the receptor and the effector can be found in the same muscle. This kind of reflex is the myotacticus reflex. It is
responsible for the control and to keep the length of the muscle and for its tension. For example the patela reflex (Fig. 3).
2) External (foreign) reflex: The meaning of the external origin is that the source of the reflex comes from the skin this implies that, the source of the stimulus the receptor is elsewhere then the effector. The main role for this reflex is to protect our system from external damage and is responsible for the sensing of heat, pain, and touch. The Sensory Epithelium is the part of the epithelium. Its role is to sense the stimulus of the outer world in our skin, it contains several kind of sensing receptor shown in figure 4. This receptors are the following:
Mechanoreceptors which respond to mechanical stimuli ( Ruffini’s end organ (sustained pressure), Meissner’s corpuscle (changes in texture, slow vibrations), Pacinian corpuscle (deep pressure, fast vibrations), Merkel’s disc (sustained touch and pressure)), Thermoreceptores responsible for heat sensation, Nocioceptors responsible for sensing extreme pain and the Free nerve endings.
Fig. 4: The mechano receptors of the hand, its receptive fild, and the response to a stimulus.
B. Gamma -loop
CNS controls the muscles via nervous runways, it manip-ulates the reflex arcs. The nervus runaways afferent fibers activates theAγmotoneurons. This neurons sense the passive elongation of the muscle. The elongation stimulate the specific receptors and they change theirs firing pattern. As a result the brain or a brain stem motoneuron activates and it activates the specific work muscle. So the gamma-loop (Fig. 5) is a system which is controlled by the CNS. Its basic functions are: posture, maintain stability, to change the intensity of the movement, exceptionally braking and acceleration and the execution of slow but sturdy movements.
IV. FINGERKINEMATICS
First of all we must define the kinematic description of the system. A hand has five fingers the Thumb, the Index, the Middle, the Ring and the Little finger. The last four are similar in structure, kinematics and constraints. The thumb has two and the other four three links.
Fig. 5: Gamma -loop
A. Kinematic configuration
Figure 6 shows the kinematic configuration of the fin-ger. Links and joints are defined as Li,j and Θi,j, where i represents a finger (i = Index, Middle, Ring, Little) and j is the appropriate link or joint. The same kine-matic configuration is used for the Index, Middle, Ring and Little finger. These configuration is define by five joints and four link, which are as follows metacarpal(Li,1), proximal(Li,3), middle(Li,4) and distal(Li,5). The joints are defined as carpometacarpal(Θi,CM C), metacarpo phalangeal is an articulation sellaris because of that it has 2 DOF’s one for the adduction–abduction (Θi,M CP a),and one for flexion–
extension (Θi,M CP f), proximal interrphalangial(Θi,P IP) and distal phalangeal (Θi,DIP).
(a) (b)
Fig. 6: The kinematic representation of the human finger.
B. Forward Kinematics
Table I shows the Denavit-Hartenberg parameters of the finger. Joint are represent by Θi,j, link are defined with ai,j
this describes the length of a phalanges. Thedi,jparameter is 0 because the length of the phalanges are fixed, and αi,j is the angle separation of Zi−1,Zi axis.
The forward kinematic of the finger is shown in equa-tion IV-B, which is based on table I.
Θi,j di,j ai,j αi,j
1 Θi,CM C 0 Li,1 π/2
2 Θi,M CP e 0 0 −π/2
3 Θi,M CP f 0 Li,3 0
4 Θi,P IP 0 Li,4 0
5 Θi,DIP 0 Li,5 0
TABLE I: The D-H parameters for a finger
Oi= −10Ti(ui)∗ 01Ti(Θi,CM C)∗ 12Ti(Θi,M CP a)
∗ 23Ti(Θi,M CP f)∗ 34Ti(Θi,P IP)∗ 45Ti(Θi,DIP) (1) Where the phrases in equation IV-B are; Oi a matrix contains position and orientation of the i− th fingertip with respect to the center of th wrist,ui vector between the center of the wrist and thei−th finger reference frame, 05Ti(Θi,j) homogeneous matrix betweeni−th finger reference frame and the finger tip. This matrix is the homogenous transformation matrix for a given phalanges.
k−1
k Ti(Θi,j) =
c(Θi,j) −c(αi,j)s(Θi,j) s(αi,j)s(αi,j) ai,jc(Θi,j) s(Θi,j) c(αi,j)c(Θi,j) s(αi,j)c(αi,j) ai,js(Θi,j)
0 s(αi,j) c(αi,j) 0
0 0 0 1
V. BIOMIMETIC FINGER TEST BED
The Biomimetic finger is designed by reproducing, as close as possible to the size and kinematics of the human finger. Figure 7a shows the first prototype of the biomimetic hands finger
The setup of a finger actuation, sensing and control is shown in Figure 7b. A finger has two actuator, the Θi,P IP,Θi,DIP
joints have one common actuator but with various ratios to achieve the linkage between the links. The Θi,M CP has one actuator in this setup the joint has only 1 DOF. Every DOF has an extensor-flexor component, this method is accomplished by one actuator just like shown in Figure 7b.
(a) (b)
Fig. 7: The testbed concept of the biomimetic finger 7b, and the finger prototype 7a.
An actuator unit contains the stepper motor, sensors
(po-65
(a) (b) (c)
Fig. 2: Human finger tendons articulations (Fig. 2a), Extensor-Flexor mechanism (Fig. 2b), Human hand muscle and tendon structure (Fig. 2c)
arranged form of connective tissues typical occurrence are tendons. Tendons are like strong braided ropes, they contains a lots of small fibers bundled to geather.
Muscles tissues are the source of force in the body due to this are we capable to move our limbs. There are three main type of muscle in the body: skeletal, smooth, cardiac. The process of movement in the hand has two parts an extensor and a flexor muscle. This way our body can move smooth and gently. Almost all degrees of freedom have its extensor flexor component.
III. CONTROL AND SENSING
The Central Nervous System (CNS) contains the spinal cord and several part of the brain. For the involuntary control of our body the main center is our spinal cord from skull down.
A. Somatic and autonomic motoric system
There are two types of control of our muscles a reflex action and a voluntary. The reflexes are not conscious they emerge from a low level of control from the spinal cord. These low level controls can be divided in two groups based on their source: muscle origin or external (skin) origin reflex.
Fig. 3: Patela reflex
1) Proprioceptive (Myotacticus) reflex: The meaning of muscle origin reflex is that the reflex source is in the skeletal muscle, the receptor and the effector can be found in the same muscle. This kind of reflex is the myotacticus reflex. It is
responsible for the control and to keep the length of the muscle and for its tension. For example the patela reflex (Fig. 3).
2) External (foreign) reflex: The meaning of the external origin is that the source of the reflex comes from the skin this implies that, the source of the stimulus the receptor is elsewhere then the effector. The main role for this reflex is to protect our system from external damage and is responsible for the sensing of heat, pain, and touch. The Sensory Epithelium is the part of the epithelium. Its role is to sense the stimulus of the outer world in our skin, it contains several kind of sensing receptor shown in figure 4. This receptors are the following:
Mechanoreceptors which respond to mechanical stimuli ( Ruffini’s end organ (sustained pressure), Meissner’s corpuscle (changes in texture, slow vibrations), Pacinian corpuscle (deep pressure, fast vibrations), Merkel’s disc (sustained touch and pressure)), Thermoreceptores responsible for heat sensation, Nocioceptors responsible for sensing extreme pain and the Free nerve endings.
Fig. 4: The mechano receptors of the hand, its receptive fild, and the response to a stimulus.
B. Gamma -loop
CNS controls the muscles via nervous runways, it manip-ulates the reflex arcs. The nervus runaways afferent fibers activates theAγmotoneurons. This neurons sense the passive elongation of the muscle. The elongation stimulate the specific receptors and they change theirs firing pattern. As a result the brain or a brain stem motoneuron activates and it activates the specific work muscle. So the gamma-loop (Fig. 5) is a system which is controlled by the CNS. Its basic functions are: posture, maintain stability, to change the intensity of the movement, exceptionally braking and acceleration and the execution of slow but sturdy movements.
IV. FINGERKINEMATICS
First of all we must define the kinematic description of the system. A hand has five fingers the Thumb, the Index, the Middle, the Ring and the Little finger. The last four are similar
First of all we must define the kinematic description of the system. A hand has five fingers the Thumb, the Index, the Middle, the Ring and the Little finger. The last four are similar