“Soft Body Robot For Physical Interaction With Humans,” Invented By Katsu Yamane, Joohyung Kim, And Alexander Nicholas Alspach. A robot designed for reducing collision impacts during human interaction. The robot includes a robot controller including a joint control module. The robot includes a link including a rigid support element and a soft body segment coupled to the rigid support element, and the body segment includes a deformable outer sidewall enclosing an interior space. The robot includes a pressure sensor sensing pressure in the interior space of the link. A joint is coupled to the rigid support element to rotate or position the link. During operations, the robot controller operates the joint based on the pressure sensed by the pressure sensor. The robot controller modifies operation of the joint from a first operating state with a servo moving or positioning the joint to a second operating state with the servo operating to allow the joint to be moved or positioned in response to outside forces applied to the link.
The present description relates, in general, to design and control of robots including humanoid robots and 
other robots adapted for interaction with humans. More particularly, the present description relates to fabrication and control of a robot with one or more body parts (or segments or modules) that are particularly adapted for soft contact and/or interaction with a human.
In order to interact with human environments, humanoid and other robots require safe and compliant control of the force-controlled joints. One way to achieve this goal is to equip the robot with torque-controlled joints, which have to be programmed to determine desired motions and output forces (contact forces) and, in response, to output joint torques to effectively control movement and positioning of the humanoid robot. However, it has proven difficult to provide wholly safe interactions between humans and robots simply by operating these humanoid and other robots with controlled movements.
As robotic systems become cheaper, more reliable, and more capable, their prevalence in our everyday environment continues to increase. Robots can be found providing interactive guidance or entertainment in stores and amusement parks and in more dynamic settings like homes, schools, hospitals, and the workplace where they teach, provide therapy, and lend an extra set of hands. In these more dynamic scenarios, robots and humans often work in close proximity where they physically interact with one another.
Where physical human and robot interaction is expected, it often is desirable for the robot’s joints and body parts to be compliant and yielding to avoid injury and damage. For example, in nursing homes, a furry seal robot has been utilized that responds to being held and pet and helps to keep our older generations socially active and engaged. Another therapeutic robot features a sensorized silicone skin that covers its underlying mechanics. While these robots respond to touch in various ways, their motion is limited. More heavily actuated robot systems (e.g., humanoid robots) have been developed that have the ability to move with a wider variety of motions and employ soft, sensorized skins to ensure human safety during physical interaction. These robot skins can sense contact in high resolution, but they involve the use of complicated electronics. In contrast, other robots have been developed that use hard plastic shells and are adapted to work safely alongside humans by using series elastic actuators to sense contacts. This sensing method also allows users to teach the robot new tasks in a natural way by guiding its limbs and end effectors, thereby sharing their workload with the robot.
The inventors recognized that there was a need for robots that can safely interact with humans and, particularly, with children. To physically interact with children, the inventors understood that the robot should be soft and durable. With this in mind, a robot physical and control design was created by the in inventors with soft and deformable body parts (or modules, segments, or the like). To test this design, the inventors developed a small toy-sized robot with soft body parts (e.g., a soft skin), and the robot was robust to playful, physical interaction. The upper body, including the arms, pelvis, chest, and back, had a plurality of fluid-filled (e.g., filled with a liquid or with a gas such as air) body parts or segments, which were each formed using 3D printing. Each body part was connected to a pressure sensor to sense contact. A controller then operated the robot differently when contact was sensed at one or more of these soft body parts to provide protection to the child (or other outside actor) and robot during the interaction.
The skin, shell, or outer sidewall of each soft body part was relatively soft and used to cover the underlying 
actuators used to drive adjacent (e.g., upstream or downstream) joints and also cover the rigid robot support elements. For example, the soft body sidewall may enclose or cover actuators and rigid, 3D-printed frame components including printed bearings (e.g., all or a portion of an adjacent joint that may be allowed to freewheel or more freely pivot/rotate about an axis when a contact is sensed on a soft body part). In this description, the soft body robot is described in detail along with discussion of the design process of the soft body parts or modules. The description also provides exemplary control processes for this soft body robot including discussion of a demonstration with the prototype soft body robot demonstrating the efficacy of the soft body parts by implementing a “grab and move” user interface for posing the robot in a link-by-link manner.
The robot design combines passive and active compliance to enhance safety during human and robot interactions. While passive compliance can be realized using deformable materials, active compliance uses sensor data to react to both expected and unexpected contacts between the robot and its environment (e.g., with an interacting human or their property). A soft robot that senses contact, as described herein, integrates these passive and active approaches to ensure human safety during physical interaction.
A robot is designed particularly for reducing impacts on collision during human interaction. The robot includes a robot controller including a joint control module (e.g., software and/or hardware operated with a processor to provide particular functionality). The robot also includes a link including a rigid support element. The body segment coupled to the rigid support element, and the body segment (or soft body part) includes an outer sidewall enclosing an interior space. The robot further includes a pressure sensor that senses pressure in the interior space of the link and also a joint coupled to the rigid support element. During operations, the robot controller operates (e.g., generates and transmits/communicates control signals) the joint based on the pressure sensed by the pressure sensor.
In some embodiments, the robot controller is configured to modify operation of the joint from a first operating state with a servo moving or positioning the joint to a second operating state with the servo operating to allow the joint to be moved or positioned in response to outside forces applied to the link. In these and other embodiments, the joint is upstream of the link in the robot (e.g., is a parent joint for the link). The outer sidewall is flexible (e.g., deformable under a human contact or under an outside compressive/contact force), whereby the interior space has a first volume in a pre-contact state and a second volume less than the first volume in a second state in which a contact force is applied to the outer sidewall. This change in volume is accompanied by an increase in pressure in the interior space. In some embodiments, the link further includes a deformation control member extending from the rigid support member to be positioned within the interior space to limit the magnitude of deformation of the outer sidewall (e.g., the link may include a rod or elongated stick with a rounded end or tip for contacting an inner surface of the outer sidewall during deformation).
In practice, the interior space is filled with a gas such as air, and the pressure measured or sensed by the pressure sensor is the pressure of the gas in the interior space, which increases from a non-contact value to a contact value (such as when a human contacts (e.g., squeezes) the outer sidewall of the link). The robot controller may operate the joint based on the pressure when the pressure exceeds a predefined threshold pressure value or when a change greater than a predefined pressure change is identified by the controller. The link may be fabricated as a single unit using a three dimensional (3D) printer (e.g., as part of a single printing process). The rigid support element may also include a connector for the pressure sensor providing a passageway to the interior space. Further, the joint may include a thrust bearing or a friction bearing that can be fabricated as a single unit using a 3D printer.