DC motors at the heart of surgical robots

At the height of the pandemic, hospitals had to postpone or cancel many elective surgeries. But now, as life starts to return to normal, facilities are facing a colossal backlog that could take five years to work through. The patients experiencing the worst delays are those waiting for knee and hip replacement surgery, with arthritis patients also bearing the brunt of the crisis.

A patient’s surgery doesn’t only involve the procedure itself — it also includes preparation to ensure that the individual is fit for surgery, then anaesthesia, the operation and finally recovery. Recovery times vary depending on the type of operation, but the longer a patient remains in a hospital bed, the longer it takes the NHS to work through its waiting list.

A helping hand

To try to tackle its waiting list crisis, the NHS has launched a £160 million investment into ‘accelerator sites’. At present, the sites are in twelve areas and five specialist children’s hospitals across the UK. Each of these facilities will receive a share of the funding to implement and evaluate innovative ways, such as the use of robotics, to increase the number of elective operations they can deliver.

Some hospitals have already adopted the use of robotics. Guys Hospital in London has recently added a fourth surgical robot to its robotic programme, making it the largest programme in the country. The £1.5 million Da Vinci robot will increase the number of surgeries performed this year by 300. Alone, this figure pales in comparison to the five million patients waiting for surgeries, but if more hospitals adopted the use of surgical robots, it would be sure to put a dent in the backlog.

When performing an operation with a robot, the surgeon sits at a console and looks at a 3D image of the operating area. They then use joysticks to move the robot’s arms, so that only the robot and surgical assistants stand over the patient. Precision is crucial in robotic surgery, and the 3D monitor means that the surgeon is able to see every detail and zoom in if required. The slim, robotic arm offers more freedom of movement when cutting, repairing or suturing compared to standard procedures.

By converting the entries made at the console, the robot is able to make incisions in the range of a tenth of a millimetre, which can’t be done by hand. This is almost the size of a grain of sand. These smaller incisions mean less blood and smaller wounds, thus speeding up recovery times.

Looking within

At the heart of surgical robots is the DC motor. These motors work by converting the electrical energy that powers the robot into mechanical energy that allows the robot to move. Inputs from the surgeon at the console are translated through the console electronics, which then provide output signals to the motors in the manipulators.

When designing surgical robots, engineers must ensure that the robots satisfy the exact speed and torque requirements and meet precise positioning demands. The ability to withstand the high temperatures of sterilisation, but remain cool during operation, is also of importance.

DC motors for surgical applications must boast a full torque at low speeds. This is important in surgical robotics, since the manipulators need full range of motion to maximise their agility and operate effectively. Compact motors make the robot more lightweight, which in-turn makes it more agile and precise.

The CR series of DC motors from FAULHABER are precision made with rare earth magnets and self-supporting rotors offering high copper fill for unrivalled performance. This makes them suitable for applications that require a compact drive solution with high torque, delivering up to 224 mNm without a gearhead in only 38mm diameter.

An ironless rotor is the central element in all FAULHABER DC motors. This improves efficiency, eliminates cogging and enhances acceleration times to give a dynamic performance and long life. These features make FAULHABER DC motors an excellent choice for surgical robots since reliability is paramount and robots cannot risk malfunctioning during surgery.

EMS is the sole supplier of FAULHABER motors in the UK. The high performance of these motors complemented by a range of gearheads and optical, magnetic or absolute encoders make them suited for medical robotic applications.

For many, it must seem futuristic to have robots operating on humans, but surgical robotics could prove to be indispensable in tackling the largest patient waiting list the NHS has ever seen. When designing robots capable of performing such intricate, precise tasks, selecting the right DC motor for the job is a crucial decision.

Stewart Goulding is managing director of precision drive system supplier Electro Mechanical Systems

http://www.ems-limited.co.uk