Table 2 Overview of lower limb EMG-driven controllers working principles

Direct control

[64]

EMG-triggered knee joint lock during stance phase

SlA\(^{\star }\), SpA\(^{\star }\)

All (STA\(^{\star }\))

NN

[29]

EMG-proportional modulation of knee joint velocity

SlA, SpA\(^{\star }\)

All (not tested)

NS

[24,25,26,27]

ML-driven knee joint angle trajectory generation

SlA, SpA

All (not tested)

CT: 10–15 s, per 2 sessions, per 5 days

[56]

EMG-driven knee joint stiffness set-point

SlA, SpA

All (NWB\(^{\star }\))

ST: 1 h, before each use

[14, 23, 62, 63]

EMG-driven knee joint stiffness set-point

SlA, SpA

All (STND\(^{\star }\), SIT\(^{\star }\), SQ\(^{\star }\), STA\(^{\star }\), NWB\(^{\star }\))

ST: 3 h, per 4 sessions; CT: 2 h trajectory tracking trials

[57]

EMG-driven multi-DoF knee and ankle joint stiffness set-point

SlA, SpA

All (NWB\(^{\star }\))

ST: therapist session; CT: 3 s per 64 trials, per 4 sessions

[37]

ML-driven knee joint angle trajectory generation

SlA, SpA

All (not tested)

NS

[16]

EMG-driven ankle joint stiffness set-point

SlA, SpA

All (NWB\(^{\star }\))

CT: 10 trials (\(\sim\) 80 s)

[67, 68]

EMG-proportional plantarflexor torque generation

SlA, SpA

All (not tested)

CT: NS

[76]

EMG-triggered ankle plantarflexion and dorsiflexion

NI

NI

CT: NS

[11]

EMG-decoded ankle and knee joint angle trajectory generation

SlA\(^{\star }\)

All (STA\(^{\star }\), STD\(^{\star }\))

CT: \(\sim\) 20 trials per task

[39, 40]

EMG-proportional plantarflexor torque generation

SlA, SpA

All

ST: limited acclimation period

Pattern recognition control

[98]

EMG-driven knee FSM (Stance [Post-HS, FF and Pre-TO], swing [SF, SE])

SlA

NI

Adaptation period of 20 min; FSM CT: NS

[70]

Knee joint moment control as function of EMG-driven locomotion identification

SlA\(^{\star }\), SpA\(^{\star }\)

STA\(^{\star }\), STD\(^{\star }\)

FSM CT: NS

[5]

EMG-driven FSM for level ground walking and stairs climbing

SlA, SpA

STA\(^{\star }\)

FSM CT: NS; ST < 20 min

[65, 66, 141, 144]

ML-driven knee joint FSM (Stance [Post-HS, Pre-TO], swing [Post-TO, Pre-HS])

SlA\(^{\star }\)

OBST\(^{\star }\), STND\(^{\star }\), STA\(^{\star }\), STD\(^{\star }\), TURN\(^{\star }\)

FSM CT: \(\sim\) 15 min (3 times each task)

[53]

CPG-generated knee and ankle joint trajectories as function of ML-driven locomotion identification

NI

STND\(^{\star }\), SIT\(^{\star }\), STA\(^{\star }\), STD\(^{\star }\)

FSM CT: NS

[85]

ML-driven knee joint FSM (Stance [Post-HS, FF, Pre-TO], swing [Post-TO, Pre-HS])

NI

STA\(^{\star }\), STD\(^{\star }\)

FSM CT: 50 gait cycles per task

[15, 110]

ML-driven knee joint FSM (Stance [Post-HS, FF, Pre-TO], swing [Post-TO, Pre-HS])

NI

NI

FSM CT: 70 gait cycles

[32, 33, 143]

ML-driven knee joint FSM (Stance [Post-HS, Pre-TO], swing [Post-TO, Pre-HS])

SlA\(^{\star }\)

STA\(^{\star }\), STD\(^{\star }\)

ST: therapist sessions; FSM CT: \(\sim\) 30s (5 times per task)

[86, 87]

ML-driven ankle joint FSM (Stance [Post-HS, Pre-TO], swing)

SlA\(^{\star }\), SpA\(^{\star }\)

STA\(^{\star }\), STD\(^{\star }\)

FSM CT: 21 trials in total, 6–7 steps per trial

[120]

ML-driven FSM for multi-DoF ankle joint

SlA, SpA

All (NWB\(^{\star }\))

FSM CT: 3 s per 8 trial, per 7 tasks

[58, 111]

ML-driven knee joint FSM (Stance [Post-HS, Pre-TO], swing [Post-TO, Pre-HS])

NI

STND\(^{\star }\), SIT\(^{\star }\), NWB\(^{\star }\)

FSM CT: NS

[59, 113, 114, 139, 140]

Knee and ankle joint impedance characterization as function of ML-driven locomotion identification

SlA\(^{\star }\)

STA\(^{\star }\), STD\(^{\star }\), SIT\(^{\star }\), NWB\(^{\star }\)

Intrinsic controller parameters tuning (NS); FSM CT: 10–20 trials per task

[17]

ML-driven ankle joint impedance characterization based terrain inclination classification

SlA\(^{\star }\)

NI

Intrinsic controller parameters tuning (NS); CT: 3 sessions; ST: \(\sim\) 5 h

[106]

EMG-triggered knee joint motion routine

NI

NI

NS

[54, 55]

ML-driven ankle joint FSM

SlA\(^{\star }\)

STA\(^{\star }\), STD\(^{\star }\)

FSM CT: 5 gait cycles per trial; ST: 5 min per task

Model-based control

[6]

EMG-driven model-based ankle joint angle trajectory generation

SlA, SpA

All (NWB\(^{\star }\))

Virtual environment training: NS

[61]

EMG-driven model-based knee joint impedance characterization

SlA, SpA

All (not tested)

CT: NS

[135, 136]

EMG-driven model-based knee joint impedance characterization

SlA, SpA

All (NWB\(^{\star }\))

CT: trajectory tracking trials, walking experiments

[71, 72, 130]

EMG-modulation of model-based ankle joint moment trajectory

SlA, SpA

All (STA\(^{\star }\), STD\(^{\star }\))

CT: 10 steps

[19]

Hybrid ML-NMS model-based knee joint moment generation

SlA, SpA\(^{\star }\)

All(STND\(^{\star }\), SIT\(^{\star }\))

CT: 3–10 trials per motor task