Evolution of robotic arms
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The foundation of surgical robotics is in the development of the robotic arm. This is a thorough review of the literature on the nature and development of this device with emphasis on surgical applications. We have reviewed the published literature and classified robotic arms by their application: show, industrial application, medical application, etc. There is a definite trend in the manufacture of robotic arms toward more dextrous devices, more degrees-of-freedom, and capabilities beyond the human arm. da Vinci designed the first sophisticated robotic arm in 1495 with four degrees-of-freedom and an analog on-board controller supplying power and programmability. von Kemplen’s chess-playing automaton left arm was quite sophisticated. Unimate introduced the first industrial robotic arm in 1961, it has subsequently evolved into the PUMA arm. In 1963 the Rancho arm was designed; Minsky’s Tentacle arm appeared in 1968, Scheinman’s Stanford arm in 1969, and MIT’s Silver arm in 1974. Aird became the first cyborg human with a robotic arm in 1993. In 2000 Miguel Nicolalis redefined possible man–machine capacity in his work on cerebral implantation in owl-monkeys directly interfacing with robotic arms both locally and at a distance. The robotic arm is the end-effector of robotic systems and currently is the hallmark feature of the da Vinci Surgical System making its entrance into surgical application. But, despite the potential advantages of this computer-controlled master–slave system, robotic arms have definite limitations. Ongoing work in robotics has many potential solutions to the drawbacks of current robotic surgical systems.
KeywordsElbow Joint Industrial Robot Surgical System Vinci Surgical System Chess Player
Although surgical robotics is in its infancy, the rapid proliferation of surgical systems attests to the fact that this technology is here to stay and that we urologists should brace ourselves for the next wave of technology that will yet again change the way we work . Many in practice are rather startled by the rapid insurgence of this sophisticated technology into the armamentarium of clinical practice. Many are overawed by the sophistication of the equipment that underlies the computer-enhanced technology that lurks “under the hood” of the da Vinci Surgical System (Intuitive Surgical, Sunnyvale, CA, USA). Yet one finds such suppositions are unfounded if one simply looks back on the steady progress leading to our current situation.
“If you will have the precision out of them, and make their fingers measure degrees like cog-wheels, and their arms strike curves like compasses, you must inhumanize them.” (J. Ruskin, The Stones of Venice )
This is a historical overview of the history of the prime robotic surgical end-effector, the robotic arm. It is hoped that such an overview will better prepare the urologist to appreciate the pedigree of the sophisticated apparatus we are currently using and, potentially, anticipate the modifications and evolution this technology has for every aspect of urologic surgical practice. History is fascinating in that insights and trends can be used to emphasize ongoing basic research efforts and develop an enlightened opinion of the overall meaning of this technology to us as urologists.
The approach in this historical review will be a bit different from that in other published accounts of robotic technology that is increasingly proliferating . The robotic arm will be the sole topic of this investigation and will be dissected rather like the human arm. Some context will be added for literary interest but the focus will be on a sequential timeline of development and how we arrived at a piano-wire based, seven degrees-of-freedom surgical system for urology that is now sweeping across the United States. The attempt is to thoroughly paint a scenario of human aspiration to achieve an augmented, human-like effector that would provide all of the advantages of mechanization and eliminate all of the potential disadvantages of the human actuator. Historical attempts before modern electrical systems will be investigated first. The joints of mechanical systems anthropomorphically reflect the human arm. The shoulder joint of modern mechanical arms will be addressed next. The elbow joint followed by the wrist will then be evaluated. Finally, the hand will be explored in all of the iterations to the present, which in some ways is the bridge from the past to present day surgical systems.
Where will all of this technology end you might ask? This technology, although in its infancy, has a historical legacy that is almost as intriguing as the software and hardware that now underlies these technological wonders. At the conclusion of this article, “cutting edge” basic research that is merging digital technology and robotics with neuroscience and cognitive research in what is often referred to as brain–machine interface systems will be presented. These fusion areas were the ultimate goals of those who began, so long ago, to dream of mechanical systems that would aid and relieve the ardors of labor and augment human performance. Nowhere in medicine is this more necessary than in surgery, where a deftly executed, minimally invasive procedure can alleviate so much pain and suffering . When all is said and done, a well crafted tale can infuse a better understanding of the potential of these enabling technologies than a scientific review of the same. As the saying goes, “Chronology is the last refuge of the feeble minded and the only resort for historians.” .
da Vinci’s robotic arm
To animate a humanoid machine he was cognizant of his need to develop a more detailed database of human kinesiology. Leonardo grounded his knowledge further with drafting, anatomy, metal working, tool making, and armor design, in addition to painting and sculpture. Leonardo was not content with a simple understanding of human anatomy, so he began to investigate and draw comparative anatomy, to better appreciate form and function. “You should make a discourse concerning the hands of each of the animals, in order to show in what way they vary.” .
In 1495, at about the time he was working on his method of painting on wet plaster and the Last Supper, da Vinci designed and probably built the first of several programmable humanoid robots. From research ongoing at the Florence-based Institute and Museum of the History of Science and work by Rosheim it is now apparent his robot could open and close its anatomically correct jaw, sit up, wave its arms, and move its head . This robot consisted of two independent systems (Fig. 1). The lower extremities had three degrees-of-freedom—legs, ankles, knees, and hips. The upper extremities had four degrees-of-freedom—arms with articulated shoulders, elbows, wrists, and hands. The orientation of the arms indicates it could only whole-arm grasp with the joints moving in unison. The device had an “onboard” programmable controller within the chest providing for power and control over the arms. The legs were powered by an external crank arrangement. The Florence-based Institute and Museum of the History of Science has developed sophisticated computer models of this design with streaming video animations. Leonardo probably returned to this design again to impress his erstwhile potential royal patron, Francis I of France. From Lomazzo’s writing about Leonardo in 1584, Francesco Melzi (one of his pupils, and heirs) states that Leonardo made several automatons from “birds, of certain material that flew through the air and a lion that could walk...the lion, constructed with marvelous artifice, to walk from its place in a room and then stop, opening its breast which was full of lilies and different flowers.” Rosheim believes that the leaf spring-powered cart could have powered the mechanical lion and his automaton knight. Leonardo’s multi-degrees-of-freedom automaton is an appropriate starting point for man’s technical interest in recapitulating form and function. da Vinci’s intense attention to detail will be a recurrent theme throughout this historical sojourn. In Leonardo’s own words, “With what words, O Writer, will you describe with like perfection the entire configuration which the drawing here does?” (da Vinci, 1513).
From automata to the Industrial Revolution
Robots of the World’s Fair
Early modern robots and robotic arms
Unimate introduced its first robotic arm in 1962 (Fig. 8) . The arm was invented by George Devol and marketed by Joseph Engelberger. The first industrial arm was installed at the General Motors plant in Ternstedt, New Jersey, for automated diecasting. Ultimately, approximately 8,500 units were sold. Industrial robots graduated from the laboratory to the factory . It is interesting that in this process the robotic arm’s movements and the degrees-of-freedom incorporated nautical terms for robotics—pitch, yaw, and roll.
The robotic arm
The shoulder joint is the highest load-bearing joint in the arm. The three degrees-of-freedom at the shoulder are pitch, yaw, and roll. The shoulder has the widest range of motion of any joint in the human body and is the foundation for most modern robotic arms. The horizontal flexion and extension (yaw) of the human shoulder is 160°. The forward flexion and hyperextension of the shoulder (pitch) is 240°. Finally, the medial and lateral rotation (roll) is 160°. In the normal human, the pitch and yaw are perpendicular to the arm, whereas the roll is in-line with the arm.
The elbow joint provides extension, retraction, reach-around, and angular reorientation of the wrist and hand. Classically, the elbow provides 150° of pitch. Many types of mechanical elbow joint have been used in robotic arm manufacture. These include telescoping, revolute (subdivided by drive-train), intermediate, remote, and direct. Of these mechanical types, the revolute is most similar to the human arm. The telescoping was an early type of robotic arm joint, it deviates much from the human anatomic concept and applications have been limited.
The wrist mechanisms developed for robotic arms were crucial in even the earliest prototypes (Fig. 9). The wrist is the end-effector terminus of the robotic arm and it allows the arm to be manipulated in three-dimensional space. Without a wrist, the mechanical arm would function more like Leonardo’s robot or some most modern crane arms. This joint is becoming increasingly complex in modern robots and is one of the fundamental features on the da Vinci Operating System. The robotic wrist is the sine qua non for high-performance robotic arms. If the human wrist moves 45° off center, ability to roll degenerates, resulting in gimbal locking. The earliest robotic applications of wrists were in the very first painting and welding robotic arms. Much more sophisticated wrists enable more dexterous teleoperated systems, but singularity problems are still a problem, and almost everyone who has used the da Vinci Surgical System has probably experienced gimbal locking of the wrist.
The hand is a “differentiated” end-effector of the robotic arm that defines the purpose and the capacity of the arm. The hand is a multi-tasking tool capable of diverse functions, for example grasping, manipulating, and pushing. A robotic hand has multiple control issues, both motor and sensory perception. Many universities are currently investigating this topic, more so than in industry.
The five principal types of robotic arm are: rectangular coordinate, polar coordinate, cylindrical coordinate, revolute coordinate, and self compliant automatic robot assembly (SCARA). Two more recent additions are called serpentine and anthropomorphic . These arms can be subdivided by the types and complexity of each of their joints and control systems. The evolution of robotic arms is rapidly developing, however, and such schemes probably do more for organizing information than in defining the actual product. Applications to medicine, and surgery in particular, are ripe for companies, because classic fields of application, for example nuclear reactor work, have declined. In the past 40 years radical improvements have been made and more degrees-of-freedom are now possible. Downsizing and cost reduction will follow. Hand technologies will rapidly advance as computer-control issues improve and work at universities will find fruitful applications in industry and medicine. “Haptics” and other sensory systems will be added to advanced surgical robotics as this technology evolves.
Some believe invasive implantable arrays are the future mode of choice which will enable our neocortex to link directly to the computers and mechanical actuators that will enable precision control. Others, however, believe this can be accomplished without surgically implantable arrays, and that the EEG has the potential to be a brain–machine interface .
The robotic arm is finally becoming the tool envisaged by those workers whose legacy started this intellectual exercise. The robotic surgical system we currently use in Urology is the “tip of the iceberg” for robotic systems . Although seemingly sprung on unsuspecting clinicians, these complex machines represent a long lineage of work beginning from early modern times and continuing to the present. Whether or not you believe this currently expensive technology will affect your practice, whether you believe you can do better yourself laparoscopically or via open surgical methods, and whether or not you believe the technology is moving faster than human social systems can handle it, there is no longer any doubt this is just the first of many potential incursions of the robotic arm into the surgical arena of the future. The robotic arm has an absolutely fascinating history of which this is just a brief glimpse.
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