IEEE Robotics & Automation Magazine - December 2017 - 83

28 March
First Trial

Overall Races
Review

Stand Up and Balancing

8 October
Cybathlon 2016

Stones

Walking
Stairs

14 May
First Day of Independent Walking
Slalom

Tilted Path
Ramp and Door

Sofa
April

May

June

July

September

August

Figure 7. The training schedule for Cybathlon 2016.

In contrast, because the joint movements in the swing
phase are larger than the joint movements in the stance phase,
as shown in Figure 5, a faster movement of the robotic leg is
required in the swing phase. In addition, the disturbances are
not significant in this phase. Therefore, the feedforward control gains, f1 and f2, and the integral control action, c 3 and s,
were activated.
The gain-scheduling method was effective, but it caused
sudden impacts when the gait phase changed. The low gain
control during the stance phase might increase the tracking
error; however, this large tracking error may cause an impulsive control input because the controller gains suddenly
become large as the swing phase starts. In such a case, the pilot
may feel discomfort and lose balance. Therefore, the jointangle trajectory was adaptively changed, such that i r, hip and
i r, knee should start from i hip and i knee in the swing phase.
Real-Time Risk Assessment and Management
Components may fail during the operation of the WalkON
Suit; these failures may or may not cause a serious problem
related to the safety of the pilot. Therefore, an automatic faultdetection algorithm continuously monitors almost all possible
risk factors in the entire robot system during operation and
provides a management plan if any failure is detected. The
risk of fault is distinguished by multiple degrees according to
severity, and the degrees of risk are defined as follows.
● Caution: The risk of a fault is minor, but operation for a
prolonged period of time without risk management can
significantly increase the risk. It is recommended that
operation of the robot be stopped within 30 min.
● Warning: The risk of a fault is meaningful, and continuous
operation without risk management can significantly
increase the risk. It is recommended that operation of the
robot be stopped within 10 min.
● Danger: The risk of a fault is critical, and continuous operation without risk management can cause an emergency situation immediately.

●

Emergency: The risk of a fault is fatal, and an injury of the
pilot may occur. It is mandatory to immediately prepare
for an accidental fall or an emergency disembarkation.

Evaluation
Training
To succeed in the powered exoskeleton race, the pilot trained
twice a week for six months, as shown in Figure 7.
1) First trial: On the very first day that the pilot wore the
WalkON Suit, he was too nervous about the awkward body
posture, as well as the mechanical sound of the robot, and
wanted to immediately stop the first trial.
2) Stand up and balancing: The pilot received intensive psychological training to overcome his fear of standing
up as well as physic a l
training to balance his
An automatic faultbody with crutches and
control the robot. He
detection algorithm
trained for a half month
in a hospital, as shown
continuously monitors
in Figure 8.
3) Walking and slalom:
almost all possible risk
During the first trial for
walking, the joint trafactors in the entire robot
jectories of a normal
gait were applied to the
system during operation.
WalkON Suit as a reference input. In normal walking, it is possible to transfer the CoG by the
natural dynamics of the human body and the ab-/
adduction movement of the hip joint and to generate
ankle-joint torque. The pilot, however, is unable to voluntarily move his legs or his waist, and thus he could not
generate the ab-/adduction motion of the hip joint and
ankle torque. Therefore, the pilot was not able to control
the CoG even, with the help of the WalkON Suit. To solve
DECEMBER 2017

IEEE ROBOTICS & AUTOMATION MAGAZINE

Table of Contents for the Digital Edition of IEEE Robotics & Automation Magazine - December 2017