In this blog post, we explore how advancements in medical robot technology are improving surgical precision and safety, and how they are overcoming human limitations.
Advances in cutting-edge computing and mechanical engineering have led to the widespread adoption of robots across various industrial sectors, boosting efficiency and reducing costs. In particular, the use of these industrial robots is expanding beyond manufacturing into numerous other fields. Robotic technology has gradually evolved to perform increasingly complex tasks, and these advancements have brought about revolutionary 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 play a crucial role even in precise tasks such as surgery. This is one example that demonstrates just how rapidly technology is advancing.
Research into the use of robots in the medical field became very active in the 1990s and began to be put into practical use. At that time, many medical professionals and engineers collaborated, focusing their efforts on developing robots that would enable more sophisticated surgeries. Medical robots, which have evolved over several generations, have now reached the fourth generation with the Da Vinci robot. The Da Vinci robot is particularly advantageous for surgeries involving prostate, rectal, esophageal, and bladder cancers, where damage to surrounding nerves and blood vessels during surgery can lead to severe side effects and complications. This is because the Da Vinci robot’s arms possess a higher degree of freedom than human arms. So, what exactly are degrees of freedom, and why does a high degree of freedom ensure an advantage in surgery?
In robotics, degrees of freedom (DOF or Mobility) refer to the number of independent variables required to describe the state of an object with minimal detail. This concept is essential for understanding complex issues related to a robot’s movement. To put it simply, think of degrees of freedom as representing the flexibility of movement. Imagine an object located in three-dimensional space. If we introduce a Cartesian coordinate system into this space, the object can move through translational motion along the x, y, and z axes, as well as rotational motion around the x, y, and z axes. All of the object’s motions can be described through combinations of these six movements, and each individual movement (for example, rotation around the x-axis) is referred to as one degree of freedom. In other words, an object located in space with no constraints has six degrees of freedom. This concept is extremely important and is considered an essential element in the design and operation of robotic arms.
So, how many degrees of freedom do two objects connected by a pin have? Although we discussed degrees of freedom above, the answer does not come to mind immediately. If dozens more objects and pins are added to this system, the problem becomes even more daunting. When calculating the degrees of freedom of such complex structures, those who have studied robotics use Grübler’s formula. This formula serves as a crucial tool for understanding complex structures and is frequently used in the process of designing and evaluating robots.
In robotics, a single object is called a “link,” and the pin connecting two links is called a “joint.” Since a joint constrains the two links, it reduces the object’s degrees of freedom. However, the degree of constraint varies depending on the type of joint, so the reduction in degrees of freedom also differs accordingly. In general, links increase degrees of freedom while joints decrease them; Grübler’s formula was developed based on this concept. No matter how complex the structure, the degrees of freedom of an object can be calculated by appropriately substituting the number of links, the number of joints, and the types of joints into Grübler’s formula. These calculations are not merely theoretical exercises; they are essential for the design and operation of robots in real-world industrial and medical settings.
By calculating the degrees of freedom in this way, we can determine how flexibly an object can move and how many actuators are needed to enable movement corresponding to those degrees of freedom. If the degree of freedom is 1, movement is possible in only one direction, but if it is 2, movement is possible in two directions. Generally, one degree of freedom requires one actuator, as a single motor is responsible for rotational or translational motion in one direction. The relationship between degrees of freedom and actuators is crucial in robot design; only when these elements are appropriately combined can a robot operate efficiently in real-world environments.
The human arm is generally said to have 7 degrees of freedom. The term “generally” is used here because this calculation assumes that the wrist and shoulder can rotate in all directions, even though they are not capable of a full 360-degree rotation. However, a robotic arm can have more than 7 degrees of freedom by adjusting the number of links and joints, and unlike the human wrist, a robotic wrist is capable of 360-degree rotation. Consequently, robotic arms can perform movements with greater flexibility than humans, allowing them to excel in fields such as medical surgery that require precise work. Furthermore, this increase in degrees of freedom allows robots to operate flexibly even in more complex environments. However, as explained above, each degree of freedom requires one actuator; thus, it is crucial to carefully balance various practical constraints—such as the robot arm’s weight, manufacturing costs, and power consumption—with the degrees of freedom required in the field to achieve an appropriate design. This goes beyond a purely theoretical issue and represents a significant challenge in developing robot systems that can be practically implemented.
