Anthropomorphic Robots and Human Interactions

1 Introduction Anthropomorphic Robots and Human Interactions John M. Hollerbach and Stephen C. Jacobsen Dept. of Computer Science & Center for Engineering Design University of Utah, Salt Lake City, UT 84112 The human has served as a focal point of robotics projects at the University of Utah s Center for Engineering Design and at its commercial offshoot, Sarcos Research Inc. Anthropomorphic robots have been created to attempt to capture human capabilities and to facilitate teleoperation by similarity of structure and performance. Animatronic figures attempt to create realistic looking and moving humans and creatures for entertainment purposes. The first author has been involved with many of these projects, either in direct development or as a user in previous institutions (McGill, MIT). The second author has been responsible for the design and construction of these humanoid and animatronic robots. This paper reviews 20 years of work at Utah in humanoid robots. Due to confines of space, we will emphasize what was done and the process, rather than technical details. Such details can be found in the references, or are proprietary in view of sponsor or company prero gatives. The key theme in these developments is that they were sponsor-driven, not just self-contained university research. Thus these robots had to satisfy sponsor goals and commercial imperatives. At the same time, we were able to derive embedded research, to extract technological and research goals along the way to satisfy ourselves. Humanoid Robot Sponsor Goals Technology Push Utah Artificial Arm Myoelectric prosthetic arm EMG-based control, impedance control Sarcos AdVAntage Arm Passive or active prosthetic arm Independent elbow, terminus control Disney robots Many DOFs, high performance Aesthetic motion, shape and color Utah/MIT Dextrous Hand Advanced hand for dexterity research High functionality, antagonistic actuation, analog controler, Condor Utah Dextrous Hand Master Teleoperation of hand Accurate measurement of angles Tactile sensors Complete sensing for hand Robust, accurate system design Navy Teleoperated System Submersible, high DOFs, force-reflecting High-performance actuation, Advanced Joint Controller Sarcos Dextrous Arm Slave Commercialization of Navy system High-bandwidth force and position control GRLA Power-line maintenance First art-to-part product Morph hand Reconfigurable vise or finger gripper Adaptability to tasks Sarcos Dextrous Arm Master Force-reflecting exoskeleton for slave Ergonomics, gravity compensation Ford robot Human-controllable display robot Portability mobility Sensor suit Whole-body goniometer Fit, calibration, DOFs Jurassic Park Dinosaurs Realistic, high-performance figures Art-to-part large designs, Digital Controller Human emulation technology Spacesuit testing Human body emulation, measurement Consider the table above, which lists the individual robots created over these years. The middle column lists the sponsor goals, while the last column lists the research issues which were addressed. We now review these robots by category. 1

2 Utah Artificial Arm The first project in humanoid robotics was the Utah Artificial Arm [12],, which is a myoelectric prosthetic arm designed for persons with amputations above the elbow (Figure 1(A)). Control is achieved by utilizing small myoelectric signals (EMGs) from antagonistic muscles of the upper arm or shoulder. The signals can control the elbow or terminal device in a proportional manner. The control system is designed to permit rapid motions of the arm where speed and stable behavior are needed for delicate, manipulative tasks. The elbow can be automatically locked and unlocked using muscle signals which also control elbow flexion. The lock allows the arm to support large loads without undue strain on the drive system or excessive electrical drain on the battery pack and for switching control from the elbow to the hand. (A) (B) Figure 1: (A) Utah Artificial Arm. (B) Sarcos AdVAntage Artificial Arm. Over 1000 Arms have been produced commercially. Research has focussed on how EMGs are to be interpreted as joint torque command signals [17]. Detailed shoulder musculature models have been developed to aid in understanding how individual muscle forces (represented by EMGs) convert to joint torque [23, 24]. Impedance control was worked out before it became popular in the robotics literature. Sarcos has developed a new upper-extremity prosthetic arm, the AdVAntage Artificial Arm (Figure 1(B)), via support from the Veteran s Administration (VA). The system is modular to permit mechanical or electrical operation. Features of mechanical operation include independent elbow and terminal device control, relatively constant force-position relationships for the elbow, and polymeric cables [16]. 3 Utah/MIT Dextrous Hand The Utah/MIT Dextrous Hand (UMDH) project began in 1981 [1] as a collaboration between the University of Utah s Center for Engineering Design (S.C. Jacobsen, PI) and MIT s Artificial Intelligence Laboratory (J.M. Hollerbach, co-pi). Several prototypes of this hand were developed [12], culminating in 1987 in the final design that was produced in 12 copies [7]. These copies are distributed among various universities and government research labs, and there is an active Users Group which meets yearly [22]. The UMDH was designed as an advanced research tool into machine dexterity. The goal in development was to devise a hand with adequate performance, so that any limitations could be ascribed to algorithms rather than hardware. The hand was designed in an anthropomorphic arrangement for two reasons: (1) to facilitate the mental mapping required for teleoperation, and (2) to profit from the existence proof of dexterity by the 2

human hand. The choice of four fingers rather than five or three, in an arrangement of three equal-length fingers and an opposing thumb, represented a compromise between the extra mechanical complexity and cost of a 5-fingered design and the added functionality over a minimal 3-fingered design such as the Stanford/JPL hand. The thumb placement is more interior to the palm than is the human thumb (Figure 2(A)). (A) (B) (C) Figure 2: (A) The Utah/MIT Dextrous Hand. (B) Remotizer and analog controller. (C) Utah Dextrous Hand Master. Each finger has three links and four joints. Each joint is actuated by two antagonistic polymeric tendon tapes, which run over pulleys to a remote actuator package. Tendon transmission is required for a slim profile for the fingers and hand, while coactivation has numerous advantages over a belt loop. Pneumatic actuators were chosen to yield a compact force source; a novel suspension jet pipe valve was designed for high performance. A remotizer mechanically decouples the 32-actuator pack from the hand, allowing the hand to be placed relatively independently from the actuator pack (Figure 2(B)). Hall-effect sensors at the finger joints were chosen because of the small size requirements, and force sensors on idler pulleys in the hand proper measure tendon force. An analog joint controller and conditioning and drive electronics are also provided. The Condor real-time architecture was devised to program and control the hand [18]. Teleoperation of the UMDH has been pursued through development of the Utah Dextrous Hand Master (UDHM). This hand master employs a novel 4-bar linkage structure to measure accurately the finger joint angles. Four joints of each of three fingers and a thumb are measured by Hall-effect sensors (Figure 2(C)). The UDHM is the second in generation of hand masters at Utah. The first employed a straight linkage design, and was subsequently commercialized by Exos Inc. Studies with the UDHM include fingertip mapping between human and robot hands and calibration of the human hand [19, 20]. One of the enduring challenges in robotics has been the development of viable tactile sensors. A full tactile sensing suite has been developed for the hand, which covers all finger segments including curved fingertips and the palm (Figure 3). The tactile sensors slip on to the finger segments, and while developed initially for the UMDH could readily be recast for other finger segment shapes. The sensor technology is comprised of capacitance sensing and arrays, defined in rubber layers. Initial designs for this tactile sensor were presented in [8]. The final design has individual tactile elements (tactels) on 2.77 mm centers, and drive-electronics located very close to each tactile pad in the finger segments. The interface electronics communicate over a serial line to an intermediate electronic interface mounted on the back of the hand, and then to an interface card on a VME bus (Figure 3(B)). Studies show that the tactile sensor has spatial localization capabilities of about 1 mm, and is capable for use in contact force control [13]. 3

(A) (B) (C) Figure 3: (A) and (B) Tactile pads. (C) Mounting on UMDH finger and palm. 4 Hydaulic Manipulators Whereas the previous robots were electromagnetically or pneumatically driven, the remainder of the robots discussed in this paper are hydraulically actuated. The reason is that hydraulic actuation is capable of far higher strength and performance than electric drives or pneumatics [2, 10]. Very high-bandwidth joint torque control is achieved with novel electrohydraulic servovalves, which have some similarity to the pneumatic servovalves in the UMDH [21], and torque sensors at every joint to linearize the joint dynamics. Anthropomorphic slave kinematics and nearly isomorphic master kinematics were chosen for easy correspondence between human and robot motions. The masters are of the exoskeleton type, to permit the natural workspace of the human arm to be employed, and to permit force reflection at the many joints of the arm and hand. 4.1 Navy Teleoperated System The Teleoperated System (TOPS) is the first of Sarcos hydraulic telemanipulators, built under contract for the Navy, and is the most comprehensive telepresence system developed to date. The dual arm, force-reflective TOPS comprises a 7-DOF arm and 9-DOF hand for both master and slave, a torso system, and a head control system (Figure 4(A)). Particularly notable is the 9-DOF, 3-fingered, force-reflecting hand (Figure 4(B)), which also contains inflatable finger mounts for safe but sturdy attachement. High-performance force control and force reflection is made possible by novel suspension-type jet pipe electrohydraulic servovalves [6]. The TOPS is meant for submersible operation at depths to 20,000 ft. An Analog Joint Controller (AJC) was developed, whose individual cards are digitally interfaced but that implement an analog servo loop. As opposed to the analog controller for the UMDH, which required pot manipulation to change gains and offsets and which was interfaced to a microprocessor system via ADCs and DACs, the AJC cards interface digitally to a microprocessor system via a parallel port. ADC operations are performed on each card for a joint s position and torque sensors. An analog PD controller has digitally writable gains; computer-generated feedforward control, such as for gravity compensation, can be added in. The slave can be directly controlled from the master, by direct connection of analog signals. 4

(A) (B) Figure 4: (A) TOPS master/slave underwater system. (B) TOPS multi-fingered force-reflecting hand. 4.2 Sarcos Dextrous Arm The Sarcos Dextrous Arm represents a commercialization of the TOPS technology. Like the TOPS, this master/slave system (Figure 5(A-B)) is hydraulically actuated and force-reflecting. The slave has 10 DOFs, including an anthropomorphic 7-DOF redundant manipulator and a 3-DOF gripper [11, 9]. It was decided to simplify the gripper over the 9-DOF TOPS hand for cost reasons. The Sarcos Dextrous Arm has torque sensors at every joint, and analog servo loops around each joint provide high-bandwidth torque control for force control, force reflection, and gravity compensation. (A) (B) (C) Figure 5: Sarcos Dextrous Arm (A) slave and (B) master. (C) GRLA arm. The Argus software package was developed for arm configuration and control, and for interfacing to the AJC. Argus ran on top of VxWorks (Wind Rivers, Inc.), which is the development environment employed for VME-based Motorola 68040 microprocessors. Methods have been developed for autonomous calibration [14] and gravity compensation of both master and slave [15]. The Sarcos Dextrous Arm exists in various combinations of master and/or slave at research labs in North America and Japan. A large-scale version of the slave arm, the GRLA, has also been developed (Figure 5(C)). The GRLA was 5

commissioned by a Canadian power utility, to explore use in remote power line maintenance. The GRLA was the first manipulator that was built without prototyping, through utilization of advanced CAD/CAM facilities (art to part). The original gripper was based on prosthetic gripper design experience. More recently, the Morph Hand has been developed to manifest the capabilities of both a three-fingered hand and a traditional vise gripper (Figure 6). The tips of two fingers are passively reconfigurable to become a vise gripper. (A) (B) (C) Figure 6: The Morph Hand in various grasping configurations, and demonstrating reconfigurability to a vise gripper. The Master has been employed both to teleoperate the Slave, and to serve as a haptic interface to a virtual reality system [3]. One project has been to interface the Master to Utah s mechanical CAD/CAM system1 [4]. A user is able to manipulate mechanical designs virtually, and feel simulated forces of contact. 5 Entertainment Robots Development of entertainment robots began in 1984 with a contract wtih Walt Disney Enterprises to increase compliance in the Lincoln figure at Disneyland. Since that time, advanced figures (both hydraulic and pneumatic) with up to 52 degrees of freedom have been developed, including moving arms, legs, torsos, necks, eyes and mouths, and are capable of facial expressions (Figure 7). Over 100 robots subsequently were manufactured for the Disney Organization. These robots can be programmed to recreate smooth, graceful, and fast human actions so effectively that they are frequently mistaken for human actors. The next generation in entertainment robots beyond the Disney robots is represented by the Ford robot (Figure 8), which has been used to introduce new Ford cars at various expositions. One of the main differences is the presence of knee motion in the Ford robot. Whereas the Disney robots were programmed manually through individual joint control knobs by animation experts, the Ford robot is controlled by an operator wearing a sensor suit (Figure 8B). Another version of a similar robot has been delivered to a theme park in Jakarta. An initial contract with Universal studios involved the redesign of the torso of the King Kong figure. Based on this success, Sarcos was chosen to build the robotic dinosaurs of Jurassic Park the Ride, at Universal Studios in Hollywood. Myriad dinosaurs, including Tyrannasaurus Rex, Stegasaurus, and Ultrasaurus, were created in greater-than-life proportions. They differed in degrees of freedom and mobility platform. One of the most significant difficulties was the development of the dinasaur skin, which had to be realistic and 6

Figure 7: Disney robots. wear well. The Jurassic Park dinosaurs represented an experiment in design in size: massive weights have to be hurtled in short time spans safely. Art-to-part was achieved with the extensive use of commercial CAD programs such as Pro Engineer. Whereas previous robots were controlled by analogy controller boards, alldigital controllers were developed for the dinosaurs. Presently, photographs of these dinosaurs cannot be shown. Figure 8: (A) Ford robot. (B) Sensor suit. 6 Human Emulation Technology A full anthropomorphic figure has been designed to test protective clothing for hazardous environments, such as spacesuits, diving suits, and suits for hazardous chemical or nuclear environments (Figure 9). This figure was created for NASA in 1994, and can test for failure, comfort, range of motion, joint load, and moisture content and temperature gradient at various phases of physical exertion. This approach replaces the sometimes dangerous and always expensive and subjective use of human test subjects. 7

Figure 9: Protective clothing tester. References [1] Hollerbach, J.M., Workshop on the Design and Control of Dexterous Hands, AI Memo 661, MIT Artificial Intelligence Lab, April, 1982. [2] Hollerbach, J.M., Hunter, I.W., and Ballantyne, J., A comparative analysis of actuator technologies for robotics, The Robotics Review 2, edited by O. Khatib, J.J. Craig, and T. Lozano-Perez. Cambridge, MA: MIT Press, pp. 299-342, 1992. [3] Hollerbach, J.M., and Jacobsen, S.C., Haptic interfaces for teleoperation and virtual environments, First Workshop on Simulation and Interaction in Virtual Environments, Iowa City, July 13-15, 1995. [4] Hollerbach, J.M., Cohen, E.C., Thompson, W.B., and Jacobsen, S.C., Rapid virtual prototyping of mechanical assemblies, NSF Design and Manufacturing Grantees Conference, Albuquerque, Jan. 3-5, 1996. [5] Jacobsen, S.C., Knutti, D.F., Johnson, R.T., and Sears, H.H., Development of the Utah Artificial Arm, IEEE Trans. Biomedical Engineering, vol. BME-29, pp. 249-269, 1982. [6] Jacobsen, S.C., Iversen, E.K., Davis, C.C., Potter, D.M., and McLain, T.W., Design of a multiple degree of freedom, force reflective hand master/slave with a high mobility wrist, in 3rd Topical Meeting on Robotics and Remote Systems, Charleston, SC, Mar. 13-16, 1989. [7] Jacobsen, S.C., Iversen, E.K., Knutti, D.F., Johnson, R.T., and Biggers, K.B., Design of the Utah/MIT Dextrous Hand, in Proc. IEEE Int. Conf. Robotics and Automation, San Francisco, pp. 1520-1532, April 7-10, 1986. [8] Jacobsen, S.C., McCammon, I.D., Biggers, K.B., and Phillips, R.P., Design of tactile sensing systems for dextrous manipulators, IEEE Control Systems Magazine, vol. 8, no. 1, pp. 3-13, 1988. [9] Jacobsen, S.C., Smith, F.M., Backman, D.K., and Iversen, E.K., High performance, high dexterity, force reflective teleoperator II, in ANS Topical Meeting on Robotics and Remote Systems, Albuquerque, NM, Feb. 24-27, 1991. 8

[10] Jacobsen, S.C., Smith, C.C., Biggers, K.B., and Iversen, E.K., Behavior-based design for robot effectors, Robotics Science, edited by Brady M.. Cambridge, MA: MIT Press, pp. 505-539, 1989. [11] Jacobsen, S.C., Smith, F.M., Iversen, E.K., and Backman, D.K., High performance, high dexterity, force reflective teleoperator, in Proc. 38th Conf. Remote Systems Technology, Washington, DC, pp. 180-185, Nov., 1990. [12] Jacobsen, S.C., Wood, J.E., Knutti, D.F., and Biggers, K.B., The Utah/MIT dexterous hand: work in progress, Int. J. Robotics Research, vol. 3, no. 4, pp. 21-50, 1984. [13] Johnston, D., Zhang, P., Hollerbach, J.M., and Jacobsen, S.C., A full tactile sensing suite for dextrous robot hands and use in contact force control, in IEEE Intl. Conf. Robotics and Automation, Minneapolis, pp. 3222-3228, April 21-28, 1996. [14] Ma, D., Hollerbach, J.M., and Xu, Y., Gravity based autonomous calibration for robot manipulators, Proc. IEEE Intl. Conf. Robotics and Automation, pp. 2763-2768, 1994. [15] Ma, D., and Hollerbach, J.M., Identifying mass parameters for gravity compensation and automatic torque sensor calibration, in IEEE Intl. Conf. Robotics and Automation, Minneapolis, pp. 661-666, April 21-28, 1996. [16] Meek, S.G., Jacobsen, S.C., and Straight, R., Development of advanced body-powered prosthetic arms, Journal of Rehabilitation Research and Development, vol. 26, no. Annual Supplement, pp. 14, 1989. [17] Meek, S.G., Wood, J.E., and Jacobsen, S.C., Model-based, multi-muscle EMG control of upperextremity prostheses, Multiple Muscle Systems: Biomechanics and Movement Organization, edited by J.M. Winters and S. L-Y. Woo. N.Y.: Springer-Verlag, pp. 360-376, 1990. [18] Narasimhan, S., Siegel, D.M., and Hollerbach, J.M., Condor: an architecture for controlling the Utah- MIT Dextrous Hand, IEEE Trans. Robotics and Automation, vol. 5, pp. 616-627, 1989. [19] Rohling, R., Hollerbach, J.M., and Jacobsen, S.C., Optimized fingertip mapping: a general algorithm for robotic hand teleoperation, Presence: Teleoperators and Virtual Environments, vol. 2, no. 3, pp. 203-220, 1993. [20] Rohling, R., and Hollerbach, J.M., Calibrating the human hand for haptic interfaces, Presence: Teleoperators and Virtual Environments, vol. 2, no. 4, pp. 281-296, 1993. [21] Smith, F., Jacobsen, S., Potter, D., and Davis, C., Miniature high performance servovalves, in Intl. Fluid Power Exposition and Technical Conf., Chicago, Mar. 24-26, 1992. [22] Utah/MIT Dextrous Hand and Sarcos Dextrous Arm Users Group web site: http://www.cs.utah.edu/ jmh/users-group.html. [23] Wood, J.E., Meek, S.G., and Jacobsen, S.C., Quantitation of human shoulder anatomy for prosthetic arm control I: Surface modelling, J. Biomechanics, vol. 22, pp. 273-292, 1989. [24] Wood, J.E., Meek, S.G., and Jacobsen, S.C., Quantitation of human shoulder anatomy for prosthetic arm control II: Anatomy matrices, J. Biomechanics, vol. 22, pp. 309-325, 1989. 9