In this blog post, we will look at how the development of medical robotics technology is improving the precision and safety of surgery and how it is overcoming human limitations.
The development of advanced computers and mechanical engineering has led to the introduction and expansion of robots in various industrial fields, increasing efficiency and reducing costs. In particular, the use of these industrial robots is expanding not only in the manufacturing industry but also in various other fields. Robotic technology has evolved to be able to perform increasingly complex tasks, and this progress has brought about innovative changes in the medical industry as well. In fact, robots, which were initially used only in large-scale manufacturing processes, have now entered the medical field and are playing an important role in precision tasks such as surgery. This is one example of how fast technology is advancing.
The use of robots in the medical field began to become very active and practical in the 1990s. At that time, many medical doctors and engineers worked together to develop robots that would enable more sophisticated surgery. Medical robots that have been developed over several generations have now reached the fourth generation, the Da Vinci robot, which is advantageous for surgery on prostate, rectal, esophageal, and bladder cancers, which can cause severe side effects and complications if the surrounding nerves and blood vessels are damaged during surgery. This is because the arms of the Da Vinci robot have a higher degree of freedom than human arms. So what is a degree of freedom, and why does a high degree of freedom guarantee an advantage in surgery?
In robotics, a degree of freedom (DOF or mobility) refers to the number of independent variables that can minimally represent the state of an object. This concept is essential for understanding the complex problems related to robot movement. To put it simply, the degree of freedom is the degree of flexibility of a movement. Let’s imagine that an object is located in three-dimensional space. If we introduce a Cartesian coordinate system into this space, the object can move in the x, y, and z-axis directions, and it can also rotate around the x, y, and z-axes. The combination of these six movements can describe all the movements of an object, and one movement (for example, rotation around the x-axis) is referred to as one degree of freedom. In other words, an object with no constraints in space has six degrees of freedom. This concept is very important and is considered an essential element in the design and use of actual robotic arms.
Then, how many degrees of freedom do the two objects connected by pins have? We have learned about degrees of freedom above, but we cannot readily come up with an answer. If dozens more objects and pins are added and connected, the problem becomes even more dizzying. When calculating the degrees of freedom of such a complex structure, those who have studied robotics use Grübler’s formula to find it. This formula is an important tool for understanding complex structures and is often used in the process of designing and evaluating robots.
In robotics, an object is called a link, and the pin connecting two links is called a joint. The joint restricts the two links, thereby reducing the degree of freedom of the object. The degree of restriction varies depending on the type of joint, so the degree of freedom reduction is also different. In any case, the idea is that links increase the degree of freedom and joints decrease it, and the Grubbler formula was developed based on this idea. No matter how complex the structure is, the Grubbler formula can be used to calculate the degree of freedom of the object by substituting the number of links, the number of joints, and the type of joints in the Grubbler formula. This calculation is not just a theoretical exercise, but is used in actual industrial and medical settings to design and operate robots.
The degree of freedom obtained in this way allows us to determine how flexible an object can move and how many power sources are needed to move it as much as possible. If the degree of freedom is 1, only one direction of movement is possible, but if it is 2, movement in two directions is possible. Generally, one degree of freedom requires one power source. This is because one motor is responsible for one direction of rotation or translational motion. The relationship between the degree of freedom and the power source is very important in the design of robots, and only when these factors are properly combined can robots operate efficiently in real-world environments.
It is said that the degree of freedom of the human arm is generally seven. The reason why we use the word “generally” here is that we calculated this figure assuming that the wrist and shoulder are not able to rotate 360 degrees perfectly, but are able to rotate in all directions. However, a robot arm can have more than seven degrees of freedom by adjusting the number of links and joints, and the wrist of a robot arm can rotate 360 degrees, unlike that of a human. Therefore, robotic arms can shine in fields such as medical surgery, which requires precise work and allows for more flexible movements than humans. In addition, this increase in freedom allows robots to operate flexibly in more complex environments. However, as explained above, since 1 degree of freedom requires 1 power source, it is important to properly design the robot arm by balancing various practical constraints such as weight, manufacturing cost, and power, and the degree of freedom required in the field. This is an important challenge in developing a robot system that can be implemented in practice, beyond simply a theoretical problem.
