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Softness. Generalization of robots. Soft robots. Research challenges. Generalization of robots. Robots are a kind of machine or dynamic system that can be reprogrammed or adjusted to do a variety of tasks while a robot is in operation A group of robots is also considered as a robot.
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Softness Generalization of robots Soft robots Research challenges
Generalization of robots • Robots are a kind of machine or dynamic system that can be reprogrammed or adjusted to do a variety of tasks while a robot is in operation • A group of robots is also considered as a robot. • Robotics: science, technology/engineering. • Robotic science: the principle of how a robot to work and how to model a robot mathematically or quantitatively. • Robotic technology/engineering: two meanings: A. how to make a robot, B. how to serve the world by robots.
Generalization of robots • A full robot includes: actuator, sensor, body, controller. • Static structure: to support load. • Mechanism: to transfer motion and force. • Machine: to transfer motion, force, and energy/power. • Robots: machine that can be changed through a program (e.g. a soft approach such as programming).
Generalization of robots Zhang et al., 2015 Bongard et al., 2007
Generalization of robots Ouyang, 2015
Softness Generalization of robots Soft robots Research challenges
Softness • Trivedi et al. (2008): “distributed deformation and theoretically an infinite degree of freedom”. • Kim, Laschi and Trimmer (2013): bio-inspired robots such as worm-like robots, caterpillar-like animals and octopus-like animals. • Rus and Tolley (2015): “systems that are capable of autonomous behavior and that are primarily composed of materials with moduli in the range of that of soft biological materials”. • Wang and Iida (2015) renamed the soft robots by “soft-matter robots” and defined it as “robotics that studies how deformation of soft matter can be exploited and controlled to achieve robotic functions”.
Softness • The above definition considers the softness in an absolute sense. Shortcoming: one can call everything as soft, as there is no absolute rigidity of matter. • No identity for soft robots, but it is simply a combination of compliant mechanisms, direct actuators, deformation-based sensor for force and displacement measurement. • Unclear about soft controller, though Wang and Lida (2015) mentioned robotic functions but not sure if control is a robotic function.
Softness • Softness is about the stress created in the environment instead of the softness of the system itself. • Softness is measured by how much the stress generated is less than the allowable stress in the environment. Benefit of such a relative softness: Design of a soft robot starts with the required softness, and then designs and constructs a robot’ body, actuator, sensor and controller.
Softness Generalization of robots Soft robots Research challenges
Soft robots • Narrow definition: • Soft robotics is the subject to study how to make use of soft objects or matters or materials to a sensor, an actuator, a controller, and a body of a robot. • Broad definition: • Soft robotics is the subject to study how to develop the basic sub-systems of a robot (i.e., sensor, actuator, body, and controller) with a controlled degree of compliance to its environment that could be humans or physical-ecological entities.
Soft robots • Different from Wang and Lida (2015) in the controller, as their robotic function does not include the controller. • E-M (E: electric; M: mechanical) direct actuators (e.g. piezoelectric actuator) do not belong to soft actuator. E-X-M (X: other energy domain than E & M) actuators do not belong to the soft actuator as well, as the electronic system is hard. • Compliant mechanisms are a kind of the soft body, as they do not involve the sensor and actuator. • E controller does not belong to the soft controller, as E is usually hard.
Soft robots Compliant mechanism is not a sot robot but a soft mechanism only
Soft robots E-based controller is not soft; therefore, the E-controller is not a soft controller
In fact, a fully soft robot is to eliminate electronics in sensor, actuator, sensor, controller. Soft robots Soft controller Fuel reservoir Actuator Wehner et al., 2016, Nature
Soft controller Soft robots Wehner et al., 2016, Nature
Soft robots • In most of the cases, a soft robot is only partially soft. • The narrow definition of the soft robot is focused on the robot itself, while the broad definition of the soft robot is focused on the softness from an environment perspective. • The narrow definition of the soft robot can be said from a structural perspective, while the broad definition of the soft robot from a functional perspective. • A complete definition of soft robots must have both the structure and function.
Soft robots Soft element Hard element at which the device interacts with human body • Soft body system • A high degree of compliance to body • Not soft body system • No compliance
Soft robots • A soft robot (its structural perspective) can be classified into • Fully soft robot (soft body, soft actuator, soft sensor, soft controller). • Partially soft robot (one of the four basic sub-systems is not soft). • Sub-systems of soft robots are: • Soft body • Soft actuator • Soft sensor • Soft controller
Softness Generalization of robots Soft robots Research challenges
Research challenges • Challenge 1: • Building blocks for soft body or mechanism • Architecture of building blocks • Operating principle • Configuration • Building blocks for compliant mechanisms can be viewed as a kind of building blocks for soft body Generalized building block: with large deformation but less stress in the block
Research challenges Design guideline 1: According to the generalized building block, a build block should be designed with large deformation but less stress in the block • Conceptual design (principle) • Embodiment design • Detailed design
Research challenges • Challenge 2: • Design and build the soft controller Wehner et al., 2016, Nature • Hardwired logic circuit • Flow system • Less studied except Wehner et al. (2016) • Distinction from flexible controller, where circuits are printed on a flexible body • Fluid or collection of particles • Power generator – chemical process Generalized controller: a system that makes decision on adjustments of power and resource in or out of a robot.
Research challenges Flexible senor • Challenge 3: • Design and build the soft sensor • The principle of soft sensor • Way of interaction • Information representation • Distinction from flexible sensor Soft sensor: no electronics is involved. Mechanical force is directly represented by a mechanical deformation Generalized sensor: a system that understands the state of a target object (robot itself, environment)
Research challenges Example of the soft actuator • Challenge 4: • Design and build the soft actuator • Architecture and principle • Power generation • Power regulation • Distinction from direct actuator Soft actuator: no electronics is involved. It is not such that electrical energy or power is converted to mechanical energy or power Generalized actuator: a system that powers and activates the motion and deformation by overcoming the damping.
Research challenges • Challenge 5: • Design and build the soft body or mechanism • Combination of building blocks into a soft body or mechanism • No research is available. • More than compliant mechanisms, though compliant mechanisms can be viewed as a kind of soft body Generalized body or mechanism: a body that is composed of several building blocks of different types
Research challenges • Challenge 6: • Integrated design and building of soft sub-systems • Sensing is completed by the spring or stiffness element. Soft sensor. • Actuation is completed by the pressure in the vessel and the spring. Soft actuator. • Controller is completed by the spring, that is, when the pressure in the vessel is higher than a value determined by the spring, the valve opens. Soft actuator. • In old days without electronics, the controller does not involve electronics but mechanical deformations only
Research challenges • Challenge 7: • Mathematical modeling of soft robots Model for behavior Analysis Synthesis or design
Discussions • The current literature seems to consider • director actuator as a soft sensor • flexible sensor as a soft sensor • flexible circuit as a soft controller • This thus fails to give an identity of soft robots. • 2. Hybrid soft and hard robots are more practical. • 3. Safety valve system can be viewed as a hybrid soft and hard robot. • 4. Generalized sensor, actuator, controller, and body or mechanism are given.
Discussions An example of building blocks for soft robots Crease changes the cardboard, which can be considered as a soft system
