Normalize EMG Signal to Maximum Within Gait Cycle

For this example, the goal is as follows:

• Process the raw EMG signal
  • In this example, a simple linear envelope was done and saved in ANALOG::ENVELOPE
• Compute the maximum of the EMG signal during each gait cycle
• Normalize the EMG signal to the maximum during each gait cycle

You can download the sample files here.

The download contains:

• Sample_Workspace.cmz with -
  • 2 Dynamic Trials
  • Processed EMG signals (ANALOG::ENVELOPE), you should use your own processing, not the example processing used to create this envelope signal
• EMG_Norm_Gait_Cycle.v3s (Example Pipeline Script)
• EMG_Norm_Gait_Cycle.v3m (Example Meta-Command)
• Call_EMG_Norm_Gait_Cycle_Meta.v3s (Example Pipeline Script calling Meta-Command)

Set_Pipeline_Parameter
/PARAMETER_NAME=R_EMG_SIGNAL_LIST
/PARAMETER_VALUE=EMG_A+EMG_B+EMG_C
! /PARAMETER_VALUE_SEARCH_FOR=
! /PARAMETER_VALUE_REPLACE_WITH=
! /PARAMETER_VALUE_PREFIX=
! /PARAMETER_VALUE_APPEND=
! /MULTI_PASS=FALSE
;

Set_Pipeline_Parameter
/PARAMETER_NAME=L_EMG_SIGNAL_LIST
/PARAMETER_VALUE=EMG_A+EMG_B+EMG_C
! /PARAMETER_VALUE_SEARCH_FOR=
! /PARAMETER_VALUE_REPLACE_WITH=
! /PARAMETER_VALUE_PREFIX=
! /PARAMETER_VALUE_APPEND=
! /MULTI_PASS=FALSE
;

Select_Active_File
/FILE_NAME=ALL_FILES
! /QUERY=
;

Event_Define_Event_Sequence
/EVENT_SEQUENCE_NAME=RCYCLE_SEQUENCE
/EVENT_SEQUENCE=RHS+RTO
! /EXCLUDE_EVENTS=
! /INSIDE_OF_SEQUENCE=
! /OFFSET_FROM_START=
! /OFFSET_FROM_END=
! /OFFSET_BY=PERCENT
/EVENT_SEQUENCE_INSTANCE=0
;

Event_Define_Event_Sequence
/EVENT_SEQUENCE_NAME=LCYCLE_SEQUENCE
/EVENT_SEQUENCE=LHS+LTO
! /EXCLUDE_EVENTS=
! /INSIDE_OF_SEQUENCE=
! /OFFSET_FROM_START=
! /OFFSET_FROM_END=
! /OFFSET_BY=PERCENT
/EVENT_SEQUENCE_INSTANCE=0
;

For_Each
/ITERATION_PARAMETER_NAME=SIDE
! /ITERATION_PARAMETER_COUNT_NAME=
/ITEMS=R+L
;

 Set_Pipeline_Parameter
 /PARAMETER_NAME=EMG_SIGNAL_LIST
 /PARAMETER_VALUE=:&:&::SIDE&_EMG_SIGNAL_LIST
 ! /PARAMETER_VALUE_SEARCH_FOR=
 ! /PARAMETER_VALUE_REPLACE_WITH=
 ! /PARAMETER_VALUE_PREFIX=
 ! /PARAMETER_VALUE_APPEND=
 /MULTI_PASS=TRUE
 ;

 ! ---------------------------------------------------------------------
 ! Get the maximum number of cycles in a trial the entire CMZ file
 ! ---------------------------------------------------------------------

 ! We're going to loop over every sequence in the trial,
 ! so first calculate the maximum number of sequences in the longest trial

 ! Count the number of cycles in each trial

 Metric_Event_Sequence_Count
 /RESULT_METRIC_FOLDER=EMG_NORM
 /RESULT_METRIC_NAME=&::SIDE&Cycle_Count
 ! /TIME_INTERVAL=
 /EVENT_SEQUENCE=&::SIDE&CYCLE_SEQUENCE
 /EXCLUDE_EVENTS=
 /GENERATE_COUNT_TOTAL_IN_GLOBAL=FALSE
 ;

 ! Calculate the maximum number of cycles across all trials
  
 Metric_Maximum
 /RESULT_METRIC_FOLDER=EMG_NORM
 /RESULT_METRIC_NAME=&::SIDE&Cycle_Count_Global
 ! /APPLY_AS_SUFFIX_TO_SIGNAL_NAME=FALSE
 /SIGNAL_TYPES=METRIC
 /SIGNAL_FOLDER=EMG_NORM
 /SIGNAL_NAMES=&::SIDE&Cycle_Count
 /COMPONENT_SEQUENCE=ALL
 /EVENT_SEQUENCE=
 /EXCLUDE_EVENTS=
 /SEQUENCE_PERCENT_START=
 /SEQUENCE_PERCENT_END=
 /GENERATE_MEAN_AND_STDDEV=FALSE
 ! /APPEND_TO_EXISTING_VALUES=FALSE
 /CREATE_GLOBAL_MAXIMUM=TRUE
 ;
  
 ! Create a list from 1 to the maximum event sequence in steps of 1

 Set_Pipeline_Parameter_From_For_Loop
 /PARAMETER_NAME=SEQUENCE_COUNT
 /PARAMETER_INDEX_START=1
 /PARAMETER_INDEX_END=GLOBAL::METRIC::EMG_NORM::&::SIDE&Cycle_Count_Global_Max
 /PARAMETER_INDEX_STEP=1
 /PARAMETER_INDEX_TYPE=INTEGER
 ;

 ! ---------------------------------------------------------------------
 ! Create Normalize Signal
 ! ---------------------------------------------------------------------

 ! Create a temporary signal which contains zeros at all frames

 Evaluate_Expression
 /EXPRESSION=CURRENT_SIGNAL * 0
 /SIGNAL_TYPES=ANALOG
 /SIGNAL_FOLDER=ENVELOPE
 /SIGNAL_NAMES=::EMG_SIGNAL_LIST
 /RESULT_TYPES=DERIVED
 /RESULT_FOLDERS=EMG_NORM_TEMP
 /RESULT_NAME=
 /APPLY_AS_SUFFIX_TO_SIGNAL_NAME=TRUE
 ;

 ! Loop over every sequence

 For_Each
 /ITERATION_PARAMETER_NAME=SEQUENCE_CURRENT
 ! /ITERATION_PARAMETER_COUNT_NAME=
 /ITEMS=::SEQUENCE_COUNT
 ;

  ! Define the "current" sequence as TEMP_CYCLE

  Event_Define_Event_Sequence
  /EVENT_SEQUENCE_NAME=TEMP_CYCLE
  /EVENT_SEQUENCE=&::SIDE&CYCLE_SEQUENCE
  ! /EXCLUDE_EVENTS=
  ! /INSIDE_OF_SEQUENCE=
  ! /OFFSET_FROM_START=
  ! /OFFSET_FROM_END=
  ! /OFFSET_BY=PERCENT
  /EVENT_SEQUENCE_INSTANCE=::SEQUENCE_CURRENT
  ;
   
  ! Loop over every EMG Signal
   
  For_Each
  /ITERATION_PARAMETER_NAME=EMG_SIGNAL_CURRENT
  ! /ITERATION_PARAMETER_COUNT_NAME=
  /ITEMS=::EMG_SIGNAL_LIST
  ;
    
   ! For all frames during the current cycle, 
   ! set the values to the maximum of the EMG signal
    
   Set_Data_To_New_Values
   /SIGNAL_TYPES=DERIVED
   /SIGNAL_FOLDER=EMG_NORM_TEMP
   /SIGNAL_NAMES=::EMG_SIGNAL_CURRENT
   ! /SIGNAL_COMPONENTS=ALL_COMPONENTS
   /RESULT_TYPES=DERIVED
   /RESULT_FOLDERS=EMG_NORM_TEMP
   /RESULT_SUFFIX=
   /EVENT_SEQUENCE=TEMP_CYCLE
   ! /EXCLUDE_EVENTS=
   ! /START_FRAME=
   ! /END_FRAME=
   ! /USE_POINT_RATE=TRUE
   /REPLACEMENT_VALUES=METRIC_MAXIMUM(ANALOG::ENVELOPE::&::EMG_SIGNAL_CURRENT&,EVENT_LABEL::SEQUENCE::TEMP_CYCLE)
   ! /THRESHOLD_HIGH=NO_DATA
   ! /THRESHOLD_LOW=NO_DATA
   ! /SET_DATA_AT_SINGLE_EVENT=FALSE
   ; 
    
  End_For_Each
  /ITERATION_PARAMETER_NAME=EMG_SIGNAL_CURRENT
  ;

 End_For_Each
 /ITERATION_PARAMETER_NAME=SEQUENCE_CURRENT
 ;

 ! ---------------------------------------------------------------------
 ! Normalize EMG Signal
 ! ---------------------------------------------------------------------

 ! Divide the EMG signals by the temporary signal above

 For_Each
 /ITERATION_PARAMETER_NAME=EMG_SIGNAL_CURRENT
 ! /ITERATION_PARAMETER_COUNT_NAME=
 /ITEMS=::EMG_SIGNAL_LIST
 ;

  Evaluate_Expression
  /EXPRESSION=ANALOG::ENVELOPE::&::EMG_SIGNAL_CURRENT& / DERIVED::EMG_NORM_TEMP::&::EMG_SIGNAL_CURRENT&
  ! /SIGNAL_TYPES=
  ! /SIGNAL_FOLDER=
  ! /SIGNAL_NAMES=
  /RESULT_TYPES=DERIVED
  /RESULT_FOLDERS=EMG_NORM
  /RESULT_NAME=&::EMG_SIGNAL_CURRENT&
  ! /APPLY_AS_SUFFIX_TO_SIGNAL_NAME=FALSE
  ;

 End_For_Each
 /ITERATION_PARAMETER_NAME=EMG_SIGNAL_CURRENT
 ;

End_For_Each
/ITERATION_PARAMETER_NAME=SIDE
;

Once the example Meta-Command from the download is placed in your Meta-Command folder, you can call the command using the following syntax:

EMG_Norm_Gait_Cycle
/EMG_INPUT_FOLDER=ENVELOPE
/EMG_OUTPUT_FOLDER=EMG_NORM
/R_EMG_SIGNAL_LIST=EMG_A+EMG_B+EMG_C
/R_EVENT_SEQUENCE=RHS+RTO
/L_EMG_SIGNAL_LIST=EMG_A_L+EMG_B_L+EMG_C_L
/L_EVENT_SEQUENCE=LHS+LTO
;

• EMG_INPUT_FOLDER should be the EMG signals you want to normalized
• EMG_OUTPUT_FOLDER should be the resulting EMG folder for the normalized signals
• R_EMG_SIGNAL_LIST the list of right side EMG signals to normalize to the right gait cycle
• R_EVENT_SEQUENCE events which indicate the right gait cycle (this example normalizes to stance, but you probably want to normalize to the entire gait cycle)
• L_EMG_SIGNAL_LIST the list of left side EMG signals to normalize to the left gait cycle
• R_EVENT_SEQUENCE events which indicate the left gait cycle (this example normalizes to stance, but you probably want to normalize to the entire gait cycle)