The actuators most used today in haptic systems are
direct-current electrical motors. They are easy to install, quiet,
and relatively simple to control. However, their reduction
mechanisms can introduce backlash and high inertia, which are
undesirable in haptic applications. In this brief, we investigate
the use of electropneumatic actuators in a teleoperation system.
Compared to the electrical actuators, pneumatic actuators
have higher force-to-mass ratio and can generate larger force
without any reduction mechanism. Moreover, they are inert to
magnetic fields, which is crucial in certain applications such
as robot-assisted surgery under magnetic resonance imaging
guidance [3], [4].
Due to the above advantages, pneumatic actuators have
been used in new applications, such as telerobotics, in recent
years. For instance, Tadano and Kawashima [5] propose a
forceps manipulator for a surgical master–slave system, which
estimates external forces without using any force sensor.
Pneumatic muscle actuators have been also recently used in
the teleoperation system [6]. They are compact and have high
power/weight density, but they are difficult to control and
require an accurate experimental characterization.
All of the prior works used proportional servovalves
in pneumatically actuated systems because they allow the
achievement of high performances in various position or force
control tasks. However, they are typically expensive because
they require high-precision manufacturing. Therefore, in this
brief, fast-switching ON/OFF valves are used due to their
advantages in terms of low cost and small size. Thanks to
the breakthroughs in valve technology such as leak reduction,
miniaturized of mechanical elements, and fast electronic components;
the solenoid valves now are faster and more accurate
than the former valves. One of the objectives of this brief is to
show that good transparency in teleoperation can be obtained
with these inexpensive components.
The traditional method for controlling a system with a
solenoid valve is pulse-width modulation (PWM) [7]–[9].
A main problem with PWM control is chattering, which is
caused by the high-frequency switching of the valve [10].
Chattering can drastically reduce the lifetime of the
valve and generate noises possibly disturbing for certain
applications.
To overcome the drawbacks of PWM-based control of
solenoid valves, this brief presents a new control method
inspired by the hybrid theory recently developed for asynchronous
and synchronous electrical motor control [11]–[13].
This approach is used in a switching-based hybrid system,
which includes continuous actuators and a discrete controller
with a finite number of states. In the case of alternating
current motor drives, contrary to conventional vector control
such as proportional-integral control in which the inverter
The actuators most used today in haptic systems aredirect-current electrical motors. They are easy to install, quiet,and relatively simple to control. However, their reductionmechanisms can introduce backlash and high inertia, which areundesirable in haptic applications. In this brief, we investigatethe use of electropneumatic actuators in a teleoperation system.Compared to the electrical actuators, pneumatic actuatorshave higher force-to-mass ratio and can generate larger forcewithout any reduction mechanism. Moreover, they are inert tomagnetic fields, which is crucial in certain applications suchas robot-assisted surgery under magnetic resonance imagingguidance [3], [4].Due to the above advantages, pneumatic actuators havebeen used in new applications, such as telerobotics, in recentyears. For instance, Tadano and Kawashima [5] propose aforceps manipulator for a surgical master–slave system, whichestimates external forces without using any force sensor.Pneumatic muscle actuators have been also recently used inthe teleoperation system [6]. They are compact and have highpower/weight density, but they are difficult to control andrequire an accurate experimental characterization.All of the prior works used proportional servovalvesin pneumatically actuated systems because they allow theachievement of high performances in various position or forcecontrol tasks. However, they are typically expensive becausethey require high-precision manufacturing. Therefore, in thisbrief, fast-switching ON/OFF valves are used due to theiradvantages in terms of low cost and small size. Thanks tothe breakthroughs in valve technology such as leak reduction,miniaturized of mechanical elements, and fast electronic components;the solenoid valves now are faster and more accuratethan the former valves. One of the objectives of this brief is toshow that good transparency in teleoperation can be obtainedwith these inexpensive components.The traditional method for controlling a system with asolenoid valve is pulse-width modulation (PWM) [7]–[9].A main problem with PWM control is chattering, which iscaused by the high-frequency switching of the valve [10].Chattering can drastically reduce the lifetime of thevalve and generate noises possibly disturbing for certainapplications.To overcome the drawbacks of PWM-based control ofsolenoid valves, this brief presents a new control methodinspired by the hybrid theory recently developed for asynchronousand synchronous electrical motor control [11]–[13].This approach is used in a switching-based hybrid system,which includes continuous actuators and a discrete controllerwith a finite number of states. In the case of alternatingcurrent motor drives, contrary to conventional vector controlsuch as proportional-integral control in which the inverter
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