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Healthcare Robotics Lab

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Now showing 1 - 10 of 12
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Whole-arm Tactile Sensing for Beneficial and Acceptable Contact During Robotic Assistance

2013-06 , Grice, Phillip M. , Killpack, Marc D. , Jain, Advait , Vaish, Sarvagya , Hawke, Jeffrey , Kemp, Charles C.

Many assistive tasks involve manipulation near the care-receiver's body, including self-care tasks such as dressing, feeding, and personal hygiene. A robot can provide assistance with these tasks by moving its end effector to poses near the care-receiver's body. However, perceiving and maneuvering around the care-receiver's body can be challenging due to a variety of issues, including convoluted geometry, compliant materials, body motion, hidden surfaces, and the object upon which the body is resting (e.g., a wheelchair or bed). Using geometric simulations, we first show that an assistive robot can achieve a much larger percentage of end-effector poses near the care-receiver's body if its arm is allowed to make contact. Second, we present a novel system with a custom controller and whole-arm tactile sensor array that enables a Willow Garage PR2 to regulate contact forces across its entire arm while moving its end effector to a commanded pose. We then describe tests with two people with motor impairments, one of whom used the system to grasp and pull a blanket over himself and to grab a cloth and wipe his face, all while in bed at his home. Finally, we describe a study with eight able-bodied users in which they used the system to place objects near their bodies. On average, users perceived the system to be safe and comfortable, even though substantial contact occurred between the robot's arm and the user's body.

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Operating articulated objects based on experience

2010-10 , Sturm, Jürgen , Jain, Advait , Stachniss, Cyrill , Kemp, Charles C. , Burgard, Wolfram

Many tasks that would be of benefit to users in domestic environments require that robots manipulate articulated objects such as doors and drawers. In this paper, we present a novel approach that simultaneously estimates the kinematic model of an articulated object based on the trajectory described by the robot's end effector, and uses this model to predict the future trajectory of the end effector. One advantage of our approach is that the robot can directly use these predictions to generate an equilibrium point control path for operating the mechanism. Additionally, our approach can improve these predictions based on previously learned articulation models. We have implemented and tested our approach on a real mobile manipulator. Through 40 trials, we show that the robot can reliably open various household objects, including cabinet doors, sliding doors, office drawers, and a dishwasher. Furthermore, we demonstrate that using the information from previous interactions as a prior significantly improves the prediction accuracy.

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Pulling Open Novel Doors and Drawers with Equilibrium Point Control

2009-12 , Jain, Advait , Kemp, Charles C.

A large variety of doors and drawers can be found within human environments. Humans regularly operate these mechanisms without difficulty, even if they have not previously interacted with a particular door or drawer. In this paper, we empirically demonstrate that equilibrium point control can enable a humanoid robot to pull open a variety of doors and drawers without detailed prior models, and infer their kinematics in the process. Our implementation uses a 7 DoF anthropomorphic arm with series elastic actuators (SEAs) at each joint, a hook as an end effector, and low mechanical impedance. For our control scheme, each SEA applies a gravity compensating torque plus a torque from a simulated, torsional, viscoelastic spring. Each virtual spring has constant stiffness and damping, and a variable equilibrium angle. These equilibrium angles form a joint space equilibrium point (JEP), which has a corresponding Cartesian space equilibrium point (CEP) for the arm's end effector. We present two controllers that generate a CEP at each time step (ca. 100 ms) and use inverse kinematics to command the arm with the corresponding JEP. One controller produces a linear CEP trajectory and the other alters its CEP trajectory based on real-time estimates of the mechanism's kinematics. We also present results from empirical evaluations of their performance (108 trials). In these trials, both controllers were robust with respect to variations in the mechanism, the pose of the base, the stiffness of the arm, and the way the handle was hooked. We also tested the more successful controller with 12 distinct mechanisms. In these tests, it was able to open 11 of the 12 mechanisms in a single trial, and successfully categorized the 11 mechanisms as having a rotary or prismatic joint, and opening to the right or left. Additionally, in the 7 out of 8 trials with rotary joints, the robot accurately estimated the location of the axis of rotation.

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A Clickable World: Behavior Selection Through Pointing and Context for Mobile Manipulation

2008-09 , Nguyen, Hai , Jain, Advait , Anderson, Cressel D. , Kemp, Charles C.

We present a new behavior selection system for human-robot interaction that maps virtual buttons overlaid on the physical environment to the robotpsilas behaviors, thereby creating a clickable world. The user clicks on a virtual button and activates the associated behavior by briefly illuminating a corresponding 3D location with an off-the-shelf green laser pointer. As we have described in previous work, the robot can detect this click and estimate its 3D location using an omnidirectional camera and a pan/tilt stereo camera. In this paper, we show that the robot can select the appropriate behavior to execute using the 3D location of the click, the context around this 3D location, and its own state. For this work, the robot performs this selection process using a cascade of classifiers. We demonstrate the efficacy of this approach with an assistive object-fetching application. Through empirical evaluation, we show that the 3D location of the click, the state of the robot, and the surrounding context is sufficient for the robot to choose the correct behavior from a set of behaviors and perform the following tasks: pick-up a designated object from a floor or table, deliver an object to a designated person, place an object on a designated table, go to a designated location, and touch a designated location with its end effector.

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Tactile Sensing over Articulated Joints with Stretchable Sensors

2013-04 , Bhattacharjee, Tapomayukh , Jain, Advait , Vaish, Sarvagya , Killpack, Marc D. , Kemp, Charles C.

Biological organisms benefit from tactile sensing across the entire surfaces of their bodies. Robots may also be able to benefit from this type of sensing, but fully covering a robot with robust and capable tactile sensors entails numerous challenges. To date, most tactile sensors for robots have been used to cover rigid surfaces. In this paper, we focus on the challenge of tactile sensing across articulated joints, which requires sensing across a surface whose geometry varies over time. We first demonstrate the importance of sensing across joints by simulating a planar arm reaching in clutter and finding the frequency of contact at the joints. We then present a simple model of how much a tactile sensor would need to stretch in order to cover a 2 degree-of-freedom (DoF) wrist joint. Next, we describe and characterize a new tactile sensor made with stretchable fabrics. Finally, we present results for a stretchable sleeve with 25 tactile sensors that covers the forearm, 2 DoF wrist, and end effector of a humanoid robot. This sleeve enabled the robot to reach a target in instrumented clutter and reduce contact forces.

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The complex structure of simple devices: A survey of trajectories and forces that open doors and drawers

2010-09 , Jain, Advait , Nguyen, Hai , Rath, Mrinal , Okerman, Jason , Kemp, Charles C.

Instrumental activities of daily living (IADLs) involve physical interactions with diverse mechanical systems found within human environments. In this paper, we describe our efforts to capture the everyday mechanics of doors and drawers, which form an important sub-class of mechanical systems for IADLs. We also discuss the implications of our results for the design of assistive robots. By answering questions such as “How high are the handles of most doors and drawers?” and “What forces are necessary to open most doors and drawers?”, our approach can inform robot designers as they make tradeoffs between competing requirements for assistive robots, such as cost, workspace, and power. Using a custom motion/force capture system, we captured kinematic trajectories and forces while operating 29 doors and 15 drawers in 6 homes and 1 office building in Atlanta, GA, USA. We also hand-measured the kinematics of 299 doors and 152 drawers in 11 area homes. We show that operation of these seemingly simple mechanisms involves significant complexities, including non-linear forces and large kinematic variation. We also show that the data exhibit significant structure. For example, 91.8% of the variation in the force sequences used to open doors can be represented using a 2-dimensional linear subspace. This complexity and structure suggests that capturing everyday mechanics may be a useful approach for improving the design of assistive robots.

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Behavior-Based Door Opening with Equilibrium Point Control

2009-06 , Jain, Advait , Kemp, Charles C.

Within this paper we present a set of behaviors that enable a mobile manipulator to reliably open a variety of doors. After a user designates a location within 20cm of the door handle, the robot autonomously locates the door handle using a tilting laser range finder, approaches the handle using its omnidirectional base, reaches out to haptically find the door, makes contact with the handle, twists it, and pushes open the door. The robot uses equilibrium point control for all arm motions. Our implementation uses a 7 DoF anthropomorphic arm with series elastic actuators (SEAs). For our control scheme, each SEA applies a gravity compensating torque plus a torque from a simulated, torsional, viscoelastic spring. Each virtual spring has constant stiffness and damping, and a variable equilibrium point. The behaviors use inverse kinematics to generate trajectories for these joint-space equilibrium points that correspond with Cartesian equilibrium point trajectories for the end effector. With 43 trials and 8 different doors, we show that these compliant trajectories enable the robot to robustly reach out to make contact with doors (100%), operate door handles (96.9%), and push doors open (100%). The complete system including perception and navigation succeeded with unlocked doors in 28 out of 32 trials (87.5%) and locked doors in 8 out of 8 trials (100%). Through 157 trials with a single door, we empirically show that our method for door handle twisting reduces interaction forces and is robust to variations in arm stiffness, the end effector trajectory, and the friction between the end effector and the handle.

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Towards an Assistive Robot that Autonomously Performs Bed Baths for Patient Hygiene

2010-10 , King, Chih-Hung , Chen, Tiffany L. , Jain, Advait , Kemp, Charles C.

This paper describes the design and implementation of a behavior that allows a robot with a compliant arm to perform wiping motions that are involved in bed baths. A laser-based operator-selection interface enables an operator to select an area to clean, and the robot autonomously performs a wiping motion using equilibrium point control. We evaluated the performance of the system by measuring the ability of the robot to remove an area of debris on human skin. We tested the performance of the behavior algorithm by commanding the robot to wipe off a 1-inch square area of debris placed on the surface of the upper arm, forearm, thigh, and shank of a human subject. Using image processing, we determined the hue content of the debris and used this representation to determine the percentage of debris that remained on the arm after the robot completed the task. In our experiments, the robot removed most of the debris (>96%) on four parts of the limbs. In addition, the robot performed the wiping task using relatively low force (<;3 N).

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Pulling Open Doors and Drawers: Coordinating an Omni-directional Base and a Compliant Arm with Equilibrium Point Control

2010-05 , Jain, Advait , Kemp, Charles C.

Previously, we have presented an implementation of impedance control inspired by the Equilibrium Point Hypothesis that we refer to as equilibrium point control (EPC). We have demonstrated that EPC can enable a robot in a fixed position to robustly pull open a variety of doors and drawers, and infer their kinematics without detailed prior models. In this paper, we extend this framework to support autonomous motion of the robot's omni-directional base both before and during pulling. With our new methods, we show that the robot can autonomously approach and open doors and drawers for which only the location and orientation of the handle have been provided. We also demonstrate that EPC can coordinate the movement of the robot's omni-directional base and compliant arm while pulling open a door or drawer, which leads to significantly improved performance. Through 40 trials with 10 different doors and drawers, we empirically demonstrated the robustness of the system. The robot succeeded in 37 out of 40 trials, and had no more than a single failure for any particular door or drawer.

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Hand It Over or Set It Down: A User Study of Object Delivery with an Assistive Mobile Manipulator

2009 , Choi, Young Sang , Chen, Tiffany L. , Jain, Advait , Anderson, Cressel D. , Glass, Jonathan D. , Kemp, Charles C.

Delivering an object to a user would be a generally useful capability for service robots. Within this paper, we look at this capability in the context of assistive object retrieval for motor-impaired users. We first describe a behavior-based system that enables our mobile robot EL-E to autonomously deliver an object to a motor-impaired user. We then present our evaluation of this system with 8 motor-impaired patients from the Emory ALS Center. As part of this study, we compared handing the object to the user (direct delivery) with placing the object on a nearby table (indirect delivery). We tested the robot delivering a cordless phone, a medicine bottle, and a TV remote, which were ranked as three of the top four most important objects for robotic delivery by ALS patients in a previous study. Overall, the robot successfully delivered these objects in 126 out of 144 trials (88%) with a success rate of 97% for indirect delivery and 78% for direct delivery. In an accompanying survey, participants showed high satisfaction with the robot with 4 people preferring direct delivery and 4 people preferring indirect delivery. Our results indicate that indirect delivery to a surface can be a robust and reliable delivery method with high user satisfaction, and that robust direct delivery will require methods that handle diverse postures and body types.

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