Table 3 Overview of the used input signals and applied processing

[64]

Single muscle not contracting during walking

NP

NI

Analog

Thresholding (Raw Sign.)

[29]

GRAC

Load cell on the knee pivot\(^{{\star } {\dag }}\); footswitch\(^{{\star } {\dag }}\);

RECT, BPF (NS)

Analog

NA (ENV)

[24,25,26,27]

Knee FLEX (RFEM/VASI/ VASL), knee EXT (SEMT)

Goniometer\(^{\star }\)

BPF (20–500 Hz)

115–192 ms

LM Network (HIST, ARC)

[56]

HAMS, QUAD

Joint encoder\(^{\dag }\) (visual feedback of knee joint position)

HPF (1st ord, 20 Hz), RECT, LPF (1st ord, 2 Hz), NORM, PCA

2 ms

QDA (ENV)

[14, 23, 62, 63]

VASL, VASM, RFEM, SEMT, BICFL

Joint encoder\(^{\dag }\) (visual and haptic feedback of knee joint position)

BPF (2nd ord, 20–450 Hz), RECT, LPF (2nd ord, 2.5 Hz), NORM; PCA

3 ms

NA (ENV)

[57]

SEMT, SAR, TFL, ADDL, GRAC, RFEM, VASM, VASL, BICFL

Joint encoder\(^{\dag }\) (visual feedback of knee joint position)

NS

200 ms

LDA (MAV, NZC, SSC, WL)

[37]

GASM/SOL, TIBA

Joint encoder\(^{\star }\)

BPF (2nd ord, 10–500 Hz), RECT, LPF (2nd ord, 10 Hz)

50 ms

NARAX (ENV)

[16]

GASM, TIBA

NP

RECT, LPF (3rd ord, 2.5 Hz); PCA

10 ms

NA (MAV)

[67, 68]

GASM/GASL

MoCap system\(^{\star }\); sensorized treadmill\(^{\star }\); control signal visual feedback\(^{{\star } {\dag }}\)

FPF (2nd ord, 100 Hz), RECT, LPF (2nd ord, 4 Hz), NORM

NS

NA (ENV)

[76]

VASM, BICFL, TIBA, GASL

Ankle goniometer\(^{\star }\), accelerometer\(^{\star }\)

RECT, LPF (NS)

NS

Peak detector (ENV)

[11]

VASL, RFEM, SEMT, BICFL

MoCap system \(^{\star }\)

NORM, BPF (4th ord, 30–350 Hz), RECT, LPF (4th ord, 6 Hz), Kalman filter

< 500 ms

NA (ENV)

[39, 40]

TIBA, GASM

Joint position\(^{{\star } {\dag }}\) (visual feedback)

HPF (2nd ord, 20 Hz), RECT, LPF (2nd ord, 2 Hz)

10 ms

NA (ENV)

[98]

GLMAX, GLMED, TFL

Footswitch\(^{{\star } {\dag }}\)

LPF (2nd ord, 1 KHz), HPF (3rd ord, 50 Hz), NORM

NS

Thresholding (ENV)

[70]

VASL, VASM, RFEM, TFL, ADDL, BICFL, SEMM, SEMT

Footswitch\(^{\star }\); load cell\(^{\star }\); MoCap system\(^{\star }\)

NS

NS

Heuristic Tree (IDE, MAV, MDF, MF)

[5]

TIBA, GASM, GASL

Footswitch\(^{{\star } {\dag }}\); potentiometer\(^{{\star } {\dag }}\); encoder\(^{{\star } {\dag }}\); class of movement performed\(^{\star }\) (visual feedback)

HPF (1st ord, 16 Hz), LPF (2nd ord, 300 Hz)

100 ms

STD

[65, 66, 141, 144]

SEMT, SAR, TFL, ADDL, GRAC, VASM, RFEM, VASL, BICFL

Footswitch\(^{\star }\), load cell\(^{{\star } {\dag }}\)

BPF (20–420 Hz)

150 ms

LDA-SVM (MAV, ZCN, WL, SSC, MEC)

[53]

RFEM, BICFL, SEMT, GASM, SOL

2× 6-axis force sensor\(^{\star }\), footswitch\(^{\star }\), joint encoder\(^{\star }\)

RMS, BPS (20–500 Hz)

NS

SVM (NS)

[85]

VASM, SEMT, ADDL, TFL

2× IMU\(^{\star }\)

NS

200 ms

Hidden Markov model (MAV, WL, ZC, SSC)

[15, 110]

VASM, ADDL, TFL, SEMT

MoCap system\(^{\star }\)

NS

NS

SVM (MAV, VAR, MDF, MPF)

[32, 33, 143]

SAR, RFEM, VASL, VASM, BICFL, BICFS, SEMT, TFL, ADDL, GRA

6-axis load cell\(^{{\star } {\dag }}\), 2× IMUs

BPF (20–420 Hz)

150–160 ms

LDA/SVM (MAV, WL, ZCN, SSC, MEC)

[86, 87]

TIBA, GASL, BICF, VASL

Footswitches\(^{{\star } {\dag }}\); IMU\(^{{\star } {\dag }}\)

BPF (4th ord, 20–500 Hz)

100–300 ms

LDA/SVM (MAV, VAR, WL, ZCN, SSC)

[120]

TIBA, PERL, GASL, GASM, VASM, VASL, RFEM, BICFL

Class of movement performed\(^{\star }\) (visual feedback)

BPF (20–450 Hz)

250 ms

LDA (MAV, ZCN, SSC, WL, ARC)

[58, 111]

BICF, RFEM, VASL, VASM, SAR, GRAC, ADDL, TFL + HAMS reinnervation

Load cell\(^{{\star } {\dag }}\), 2× joint encoders\(^{{\star } {\dag }}\), 2× IMU\(^{{\star } {\dag }}\)

BPF (20–450 Hz)

250 ms

same as [140] + Euristic FSM (MEC)

[59, 113, 114, 139, 140]

SEMT, ADDL, TFL, RFEM, BICFL, SAR, GRAC, VASL, VASM

Load cell\(^{{\star } {\dag }}\), 2× joint encoders\(^{{\star } {\dag }}\), 2× IMU\(^{{\star } {\dag }}\)

BPF (20–450 Hz)

250–300 ms

LDA/DBN (MAV, WL, ZCN, SSC, 6ord ARC, MEC)

[17]

GASM, TIBA

Load cell\(^{{\star } {\dag }}\), joint angle encoder\(^{{\star } {\dag }}\), 2× IMU\(^{{\star } {\dag }}\)

PCA

200 ms

LDA (MAV)

[106]

GASL/SOL

NP

NI

NS

Thresholding (Raw Sign.)

[54, 55]

FIBL, BICF

NP

BPF (4th ord, 20–500 Hz)

256 ms

LDA/SVM/NN (38 mixed domain features)

[6]

GASL, SOL, TIBA

Joint angle\(^{{\star } {\dag }}\) (visual feedback)

LPF (7th ord, 5 Hz), NORM

\(\sim\) 1 ms

NA (ENV)

[61]

VASL, BICFL

NP

BPF (20–450 Hz), RECT, LPF (5/10 Hz), NORM

NS

NA (ENV)

[135, 136]

HAMS, QUAD

Load sensors\(^{{\star } {\dag }}\), goniometer\(^{\star }\)

BPF (7th ord, 20–1000 Hz), RECT, LPF (5 Hz)

NS

NA (ENV)

[71, 72, 130]

GASM, TIBA

Joint encoder\(^{{\star } {\dag }}\), torque sensor\(^{{\star } {\dag }}\), 6× load cells\(^{{\star } {\dag }}\)

HPF(4th ord, 80 Hz), RECT, AVR

150–200 ms

NA (ENV)

[19]

VASM, VASL, RFEM, BICF, SEMT

MoCap system\(^{\star }\), sensorized treadmill\(^{\star }\), 2× IMU\(^{{\star } {\dag }}\)

BPF (2nd ord, 30–300 Hz), RECT, LPF (2nd ord, 6 Hz), NORM

300 ms

NA (ENV)