This work is supported by NWO, Domain Applied and Engineering Sciences, Project no. 14429.
The inverted Muscle Skeleton approach
Moving beyond rigid exoskeletons
References
[1] A. T. Asbeck, S. M. De Rossi, K. G. Holt, and C. J. Walsh, “A biologically inspired soft exosuit for walking assistance”, 2015.
iMS Knee Extension Prototype Schematic
iMS Knee Extension Prototype Realisation
iMS Prototype Evaluation
Pneumatics and Sensor Schematic
Martijn E. Grootens* Edsko E.G. Hekman Herman van der Kooij
Department of Biomechanical Engineering, University of Twente, The Netherlands.
*m.e.grootens@utwente.nl
Actuators
Push between body segments
Shear forces
Their direction is now inverted
Shear forces carried by straps
→ No shear forces on the wearer → Only compression forces on wearer
iMS Approach
Artificial muscles
Pull between body segments
Small artificial muscle moment arms
→ Large actuator forces
Large shear forces
→ Shear forces act on the wearer
→ Torques limited by the shear forces the wearer can support [1]
Exosuits Approach
Cable Cable Actuator Actuator Waist belt Proximal shell Pneumatic cylinders Strap Hip axis Ankle axis Proximal axis Knee axis Distal axis Flexible rod Distal shell Strap Padding PaddingSuccessful application of iMS approach to knee orthosis design
– Knee extension torque up to 42 Nm
– Range of motion up to 62 degrees (flexion)
Challenges
– Keeping in place during walking
Other possible iMS applications
– Ankle plantarflexion – Upper extremities
Discussion and Conclusion
Assistance ‘strategy’
Virtual compression spring on prototype cylinders, while doing one-legged squats.
ɛ
3/2-W
ay
5/3-W
ay
50L Supply
P
SMain valve Prop. dir. Valve
Cylinders
P
1P
2ɛ
Proximal hinge
ƒ
1Distal hinge
ƒ
2Extensor muscles
Normalized time [-] Scaled mean
1111111111111111111111111 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 1111111111111111111111111 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 1111111111111111111111111 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 V as.La t. Vas.Med. Rec.F em.
Muscle Activity (EMG)
Cylinder position ɛ and actuator force Fa ; Tracking of reference force Fr
Time [s]
0
0.05
0.1
0.15
0
20
40
60
0
200
400
F or ce [N] P ositionɛ
[m] Force Tracking Fr FaSquat motion: extension–flexion–extension
Normalized time [-] 1111111111111111111111111 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 99 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 1111111111111111111111111 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 1. 02 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 0. 97 1111111111111111111111111 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 9 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 0. 74 Position
ɛ
[m] 0% 50% 100% Assistance level Motion Profile MusclesPull between body segments
Small muscle moment arms
→ Large muscle forces
Large compression forces
→ Compression forces on bones
Musculoskeletal System
Quadriceps
Calf
