**1. Introduction**

252 Serial and Parallel Robot Manipulators – Kinematics, Dynamics, Control and Optimization

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Robots are well established in science and technique. They are used in different environments and they have different structures. Typical robot movements are rapid and steepy when the movement direction changes occurs. It is not necessary to replicate a biological nature based solution for most tasks, so such movements are acceptable and simpler to obtain. Control algorithms are simpler for such cases, development and settings of such controllers are more straightforward.

Robots are also based on a set of joins and serial or parallel configurations. Different configurations are usefully for selected task and may be not based on biological nature references. Replication of biological nature are not necessary, and for example a wheels that are simple to design have not biological references.

Join based approach of robot design is well established and there are many technical advantages of such structure (Fig. 1). Mechanic of the robots is based mostly on a kind of the skeleton. The endoskeletons design uses a mechanical parts located inside light–weight casing. The exoskeletons design uses a mechanical parts that is casing also. Some robots uses mixed design, where the 'bones' are in endosceleton design and only joints uses exosceleton design. Exosceletons design are used in hostile environments typically.

Fig. 1. Rigid actuator

The bones are fixed, so length of the bone or its curvature is not possible to change. Additional actuators for arm extension are used sometimes. Fixed structure of the robot, even if redundant number of degrees of freedom is available, is convenient for analysis and design.

The Electroactive Polymers (EAPs) are the most promising materials for non–rigid robots design nowadays. The advantages of such materials are applied for rigid robots also, because it is important replacement of the electrical motors. Improved reliability, increased lifetime, reduction of electromagnetic emission are very important for robot design. There are many materials based on the different effects [ Bar–Cohen (2004); Besenhard et al. (2001); Capri & Smela (2009); Chanda & Roy (2009); Hu (2007); Kim & Tadokoro (2007); Otake (2010); Wallace et al. (2009)]. The Electronic EAPs uses piezoelectric, electrostatic, electrostrictive and ferroelectric effects nowadays. The Ionic EAPs uses the displacement of ions inside the

255

One of the most important task is the measurement of the state of such robot or manipulator. The conventional position and orientation approach is not well fitted, because non–rigid robots are flexible, so huge or infinite number of positions points are possible. Moreover, the estimation of the number of degrees–of–freedom by the simple visual observation of robot

The reasonable way is to estimate position and orientation in some points, especially for the end–effector and limited number of selected intermediate points. The overall estimation is possible, using the model based techniques and vision measurements. The vision techniques are well suited for such robots, because they make measurements in hundreds or millions

The open–control loop, without knowledge about achieved state, is applicable for very specific cases only, for non–rigid robots. The flexibility of the non–robots have important disadvantage – the forces from manipulated objects and forces from environments influent on the achieved state. Such forces change state and in the worst case all points of the non–rigid robots may differ between the expected position and real one. This is one of the reasons why the closed–control loop for rigid robots and the state estimation are necessary. Vision based technique for rigid robots (visual servoing [ Agin (1979); Chaumette (1998); Chaumette & Hutchinson (2008); Corke & Hutchinson (2001); Fung & Chen (2010); Malis at al. (1999); Marchand at al. (2005); Sanderson & Weiss (1983)]) are used from many

Different video tracking schemes for non–rigid robots and actuators are possible, and the

Conventional motion capture system (multiple camera vision system [ Aghajan & Cavallaro (2009)]) uses a set of cameras located around robot (Fig. 3). Video tracking gives abilities of the robot state estimation what is necessary to control. Such system is very simple for implementation in comparison to other presented tracking schemes. The market availability of such systems for large working area (known as a volumen) like a cubic area with a few meters distance in every direction is important for large scale systems. There are also available

Typical motion capture system uses markers for estimation of the state of human or some objects. The measurements are contact less so significant integration or embedding into robot surface is not necessary. The weight of the robot is preserved. Motion capture system may be used for measurements a very large number of points located on the robot surface. Single or

There are also drawbacks related to the vision techniques. Occlusion reduces a possibility of the state estimation, and the multiple cameras are necessary for reduction of such effects, but

years, and it is very promising technique for non–rigid robots also.

systems for small working area about half meter in every direction.

a few cameras are sufficient for estimation of the robot state in most cases.

polymer.

movements is not feasible.

points (pixels in extended cases).

Estimation of Position and Orientation

for Non–Rigid Robots Control Using Motion Capture Techniques

**3. Visual systems for non–rigid robots**

**3.1 Conventional motion capture system**

selected are presented shortly.

#### **2. Non–rigid robots**

Rigid structure is not only–one solution for the robots. The flexible (non–rigid, elastic) robots, complete actuators, and partially flexible actuators are also important for the future robots (Fig. 2). Flexibility of the actuators or overall robot's body is inspired by the biological nature. The giant amount of the species that live in different environments uses flexible bodies or bodies parts with evolutionary success.

Fig. 2. Non–rigid actuator

Non–rigid robots are active and open research area. Any physical effect related to the flexible movement that is driven by the any factor (continuously or PWM–like) may be applied for intentional movement of robot or actuator. Direct or indirect control of the movement by the electrical signal is desired especially. The Pulse Width Modulation (PWM) control is especially important for simplification of driver.

The pneumatic[ Daerden (1999); Daerden & Lefeber (2002); Verrelst (2005)] or hydraulic effects may be used, but the control of them is possible by the electric–to–pneumatic or electric–to–hydraulic conversion devices and is indirect control. The bimetal or memory alloy actuators are controlled by the electricity more directly (exactly there is an electrical energy–to–heat conversion but no additional devices like pumps are necessary).

Progress in the material engineering and market availability of materials, that are sensitive on electricity, gives an ability of application such 'muscles' for skeleton based robots, or even a build an complete body of non–rigid robots.

Non–rigid robots may be characterized by the place of movement. In the rigid robot the movement points are defined by the main gear axis or motor axis. For linear movement the line of the movement is also well defined like for the linear stepping motors for example. Conversion of rotary to linear movement is also used.

The non–rigid robots may be controlled in a hundreds points per muscle. The conventional classification and comparison of actuators, based on the number of degree–of–freedom, is not convenient for such cases. Electrical based control of Electroactive Materials gives building abilities of robots and controlling them in so many of points, giving a new way of robots design. Such robots may change external shape and size (morphing robots).

A few main types of Electroactive Materials are used and developed nowadays.

The simplest are the bimetal strips and coils based on the conversion of electrical energy into heat. The Shape Memory Alloys are also interesting alternatives to bimetal, and the best know is the Nitinol (Nickel titanium). The more advanced actuators like Biometal helix, due significant length changes are also important. The Nitinol was applied in well know Stiquitio hexapod robot legs and derivatives [ Conrad & Mills (2004)]. The main drawback of the bimetal and SMA is the speed of the physical changes that is about a few seconds depending on material and design. Heating of such material is controlled by the electricity and could be very rapid, but cooling is depends on the environment of the work.

2 Will-be-set-by-IN-TECH

Rigid structure is not only–one solution for the robots. The flexible (non–rigid, elastic) robots, complete actuators, and partially flexible actuators are also important for the future robots (Fig. 2). Flexibility of the actuators or overall robot's body is inspired by the biological nature. The giant amount of the species that live in different environments uses flexible bodies or

Non–rigid robots are active and open research area. Any physical effect related to the flexible movement that is driven by the any factor (continuously or PWM–like) may be applied for intentional movement of robot or actuator. Direct or indirect control of the movement by the electrical signal is desired especially. The Pulse Width Modulation (PWM) control is especially

The pneumatic[ Daerden (1999); Daerden & Lefeber (2002); Verrelst (2005)] or hydraulic effects may be used, but the control of them is possible by the electric–to–pneumatic or electric–to–hydraulic conversion devices and is indirect control. The bimetal or memory alloy actuators are controlled by the electricity more directly (exactly there is an electrical

Progress in the material engineering and market availability of materials, that are sensitive on electricity, gives an ability of application such 'muscles' for skeleton based robots, or even a

Non–rigid robots may be characterized by the place of movement. In the rigid robot the movement points are defined by the main gear axis or motor axis. For linear movement the line of the movement is also well defined like for the linear stepping motors for example.

The non–rigid robots may be controlled in a hundreds points per muscle. The conventional classification and comparison of actuators, based on the number of degree–of–freedom, is not convenient for such cases. Electrical based control of Electroactive Materials gives building abilities of robots and controlling them in so many of points, giving a new way of robots

The simplest are the bimetal strips and coils based on the conversion of electrical energy into heat. The Shape Memory Alloys are also interesting alternatives to bimetal, and the best know is the Nitinol (Nickel titanium). The more advanced actuators like Biometal helix, due significant length changes are also important. The Nitinol was applied in well know Stiquitio hexapod robot legs and derivatives [ Conrad & Mills (2004)]. The main drawback of the bimetal and SMA is the speed of the physical changes that is about a few seconds depending on material and design. Heating of such material is controlled by the electricity

energy–to–heat conversion but no additional devices like pumps are necessary).

design. Such robots may change external shape and size (morphing robots). A few main types of Electroactive Materials are used and developed nowadays.

and could be very rapid, but cooling is depends on the environment of the work.

**2. Non–rigid robots**

Fig. 2. Non–rigid actuator

important for simplification of driver.

build an complete body of non–rigid robots.

Conversion of rotary to linear movement is also used.

bodies parts with evolutionary success.

The Electroactive Polymers (EAPs) are the most promising materials for non–rigid robots design nowadays. The advantages of such materials are applied for rigid robots also, because it is important replacement of the electrical motors. Improved reliability, increased lifetime, reduction of electromagnetic emission are very important for robot design. There are many materials based on the different effects [ Bar–Cohen (2004); Besenhard et al. (2001); Capri & Smela (2009); Chanda & Roy (2009); Hu (2007); Kim & Tadokoro (2007); Otake (2010); Wallace et al. (2009)]. The Electronic EAPs uses piezoelectric, electrostatic, electrostrictive and ferroelectric effects nowadays. The Ionic EAPs uses the displacement of ions inside the polymer.

One of the most important task is the measurement of the state of such robot or manipulator. The conventional position and orientation approach is not well fitted, because non–rigid robots are flexible, so huge or infinite number of positions points are possible. Moreover, the estimation of the number of degrees–of–freedom by the simple visual observation of robot movements is not feasible.

The reasonable way is to estimate position and orientation in some points, especially for the end–effector and limited number of selected intermediate points. The overall estimation is possible, using the model based techniques and vision measurements. The vision techniques are well suited for such robots, because they make measurements in hundreds or millions points (pixels in extended cases).

The open–control loop, without knowledge about achieved state, is applicable for very specific cases only, for non–rigid robots. The flexibility of the non–robots have important disadvantage – the forces from manipulated objects and forces from environments influent on the achieved state. Such forces change state and in the worst case all points of the non–rigid robots may differ between the expected position and real one. This is one of the reasons why the closed–control loop for rigid robots and the state estimation are necessary. Vision based technique for rigid robots (visual servoing [ Agin (1979); Chaumette (1998); Chaumette & Hutchinson (2008); Corke & Hutchinson (2001); Fung & Chen (2010); Malis at al. (1999); Marchand at al. (2005); Sanderson & Weiss (1983)]) are used from many years, and it is very promising technique for non–rigid robots also.
