Medical Design Briefs - April 2024 - 18

Design Briefs
Designing the Right Motor to Enhance Surgical
Robot Precision
Exploring key considerations in motor design to improve a robotic motion
system's precision during critical surgical procedures.
By Paul Schonhoff, Portescap
surgical robot's precision is critical
to the success of the surgery -
and to the outcome of the patient.
Advances in motion system technology
will go a long way toward improving
surgical robotic precision, unlocking
opportunities for previously high-risk
procedures, enabling new minimally
invasive surgical techniques, reducing
damage to tissue and facilitating patient
recovery times.
A
Central to the motion system that will
make these and other benefits possible
is the electric motor. However, not all
motors are created equal - especially
where surgical robots are concerned.
For example, it's important to choose
motors that have a zero-cogging brushless
DC design and slotless structure,
both of which improve robotic control
and responsiveness. Coupled with the
right specifications related to the power
density, encoder and autoclavable capabilities,
this brushless DC motor has the
potential to redefine existing standards
of precision and performance in robotic
surgeries.
To explore this topic further, the
following article highlights the steps
designers should take when specifying
their motor and motion system for use
in surgical robot applications.
How Robotic Precision Enhances
Patient Outcomes
Improving the precision of surgical
robots has the potential to increase the
effectiveness of the surgery, advance patient
outcomes and enable procedures
that were previously considered too
high risk. Better tool control would reduce
the risk of damage to vital organs
and arteries close to the surgical site.
Similarly, smaller incisions would minimize
the area of damage to healthy
tissue. Even for robotic surgical procedures
considered " standard, " enhancing
precision would improve patient
18
Improving the precision of surgical robots has the potential to enable procedures that were previously considered
too high risk. (Credit: Portescap)
recovery. The less invasive the surgery,
the less time it would take someone to
heal. There would also be less scarring
from smaller incisions, reducing the risk
of future complications.
The Central Role of the Motion
System
Ongoing developments to improve
the precision of surgical robots tend to
focus on the end effectors that hold and
operate tools like blades and grinders.
Central to the end effectors' performance
is the motion system that drives
and controls the components - specifically,
the motor that controls the end
effector's speed and position. In order
to deliver smooth torque, which is essential
to the robot's precision, the motor
must overcome cogging, or the periodic
variation in torque resulting in ripples
during rotation.
While cogging can result in jerky
motion, it can also reduce the motor's
www.medicaldesignbriefs.com
responsiveness to control commands.
Delays in achieving the end effector's
desired position or trajectory will inhibit
haptic feedback and decrease the robot's
control. Due to this outcome, it is
critical to specify a motor that can deliver
as close to zero cogging as possible in
order to optimize precision and achieve
real-time responsiveness during robotic
surgeries.
A Closer Look at Zero-Cogging
Motor Designs
Brushless DC (BLDC) motors are preferred
when it comes to smooth torque
delivery. A BLDC motor uses electronics
to achieve commutation - the process
of switching the direction of current
flow in the motor's coils to maintain continuous
rotor rotation. Electronic commutation
can also include integrated
Hall sensors to optimize feedback and
control of the electromagnetic circuit.
This design is typically smoother comMedical
Design Briefs, April 2024
http://www.medicaldesignbriefs.com
Medical Design Briefs - April 2024

Table of Contents for the Digital Edition of Medical Design Briefs - April 2024
