Humans show increased systematic and random errors when reaching for targets at 3.8Gx with or without added vibration

Adelstein, Bernard D.

Liston, Dorion B.

Stone, Leland S.

NASA Technical Reports Server

Reaching	  Errors	  Under	  G-­‐Loading	  
(and	  vibra6on)	  	  
Bernard	  D.	  Adelstein,	  Dorion	  B.	  Liston,	  Leland	  S.	  Stone	  
	  
Human	  Systems	  Integra/on	  Division	  
NASA	  Ames	  Research	  Center	  
https://ntrs.nasa.gov/search.jsp?R=20160004751 2019-08-31T03:51:31+00:00Z
Dual	  Display	  Touchscreen	  Panel	  
With	  High-­‐Resolu6on	  High-­‐Frame-­‐Rate	  Camera	  
•  Apple	  30-­‐inch	  HD	  Cinema	  Displays	  equipped	  w/	  touchscreen	  
•  2560	  X	  1600	  pixels	  (ver6cal	  X	  horizontal)	  per	  panel	  
•  100	  pixel/inch	  resolu6on	  (30	  pixel/deg	  visual	  angle)	  
•  Viewing	  Distance	  18	  in	  
Sample	  Raw	  Data	  (One	  Par6cipant,	  3.8-­‐G	  Bias,	  Zero	  Vibra6on)	  
•  Three	  target	  zones	  each	  panel	  
•  Target	  zone	  diameter:	  3.6	  inch	  (360	  pixels)	  	  
•  Ver6cal	  zone	  separa6on:	  3.6	  inch	  (360	  pixels)	  center-­‐center	  
•  Horizontal	  zone	  separa6on:	  19.4	  inch	  center-­‐center	  (~±30°	  visual	  from	  midline)	  
o	  -­‐	  target	  
+	  -­‐response	  
Lateral	  
Fo
ot
w
ar
d	  
Manual	  Poin6ng	  Response	  Time	  by	  Target	  Zone	  
(and	  by	  block)	  
•  3.8	  Gx	  load	  slows	  response	  by	  about	  150ms	  
•  Slower	  responses	  to	  contralateral	  and	  upper	  targets.	  
700	  
800	  
900	  
1000	  
1100	  
1200	  
1300	  
UL	   ML	   LL	   UR	   MR	   LR	  
Re
sp
on
se
	  T
im
e	  
(m
s)
	  
Target	  Zone	  
N	  =	  10	  observers,	  mean±SEM	  
Leg	  
(contralateral)	  
Right	  
(ipsilateral)	  
3.8	  G	  
1.0	  G	  
1	  
2	  
3	  
Bl
oc
k	  
	  
Systema6c	  Ver6cal	  Response	  Error	  
•  Signiﬁcantly	  greater	  systema6c	  footward	  error	  at	  3.8	  Gx	  
•  More	  pronounced	  for	  lower	  ipsilateral	  (right)	  targets	  
•  ~0.75	  inch	  for	  95%	  conﬁdence	  
N	  =	  10	  observers,	  mean±SEM	  
-­‐10	  
0	  
10	  
20	  
30	  
40	  
50	  
60	  
70	  
UL	   ML	   LL	   UR	   MR	   LR	  
Ve
r6
ca
l	  e
rr
or
	  (0
.0
1	  
in
ch
)	  
	  
Target	  Zone	  
3.8	  G	  
1.0	  G	  
Fo
ot
w
ar
d	  
30	  
40	  
50	  
60	  
70	  
80	  
0	   8	   12	   16	  
Vibra6on	  Frequency	  (Hz)	  
20	  
30	  
40	  
50	  
60	  
70	  
80	  
UL	   ML	   LL	   UR	   MR	   LR	  
di
sp
er
si
on
	  (0
.0
1	  
in
ch
)	  
	  
Target	  Zone	  
Ver6cal	  Response	  Precision	  (Error	  Dispersion)	  	  
N	  =	  10	  observers,	  mean±SEM	  
3.8	  G	  
1.0	  G	  
0	   0	  
3.8	  G	  
1.0	  G	  
•  Greater	  ver6cal	  random	  error	  (dispersion)	  at	  3.8	  G	  and	  for	  lower	  targets	  
•  ~1.2	  inch	  radius	  for	  95%	  conﬁdence	  
•  Dispersion	  increase	  at	  elevated	  G	  is	  largely	  independent	  of	  vibra6on	  
An	  ergonomic	  study	  by	  Schafer	  and	  Bagian	  indicated	  that:	  	  
1)  Signiﬁcant	  reduc/on	  in	  forward	  and	  upward	  arm	  range-­‐of-­‐mo/on	  occurred	  at	  4Gx	  &	  above,	  	  
2)  “The	  variance	  exhibited	  by	  the	  large	  standard	  errors	  is	  most	  likely	  the	  direct	  result	  of	  the	  
diﬃculty	  in	  performing	  purposeful	  movement	  during	  high	  G-­‐loads”,	  and	  
3)  Several	  crew/aviator	  par/cipants	  declined	  to	  perform	  the	  task	  above	  4	  Gx.	  
	  	  
A	  human-­‐performance	  study	  Ames	  examining	  reach	  accuracy/precision	  during	  3.8Gx	  loading	  
plus	  vibra/on	  found	  that:	  
1)  Reaches	  showed	  increasing	  systema/c	  error	  as	  they	  became	  more	  footward,	  
2)  Systema/c	  errors	  were	  as	  high	  as	  0.75	  inches,	  
3)  Random	  errors	  were	  as	  high	  as	  1.2	  inches,	  
4)  Worst-­‐case	  total	  error	  is	  therefore	  <	  2	  in	  (~95%	  conﬁdence)	  for	  reaches	  with	  forward	  
component	  of	  around	  10	  inches	  with	  prac/ce	  (training)	  and	  no	  de-­‐condi/oning.	  
	  
Gx	  accelera/ons	  generate	  both	  resis/ve	  forces	  that	  hold	  the	  arm	  back	  and	  lateral	  forces	  that	  
torque	  the	  arm	  away	  from	  the	  correct	  trajectory.	  	  The	  30-­‐deg	  limit	  was	  established	  somewhat	  
arbitrarily	  because	  sin(30	  deg)	  =	  0.5.	  	  Thus,	  this	  limit	  deﬁnes	  the	  point	  at	  which	  the	  lateral	  forces	  
represent	  50%	  of	  the	  total	  G-­‐force,	  i.e.,	  at	  3	  Gx,	  outside	  of	  the	  cone,	  there	  is	  at	  least	  a	  1.5g	  force	  
pulling	  the	  arm	  (torqueing	  the	  shoulder)	  away	  from	  the	  desired	  target.	  	  That	  said,	  the	  30-­‐deg	  
limit	  does	  appear	  to	  ﬁt	  with	  desired	  reach	  errors	  being	  smaller	  than	  2	  inches.	  
Forward	  work:	  Convert	  the	  reach	  data	  herein	  to	  angular	  posi/ons	  in	  shoulder	  coordinates	  
(which	  could	  poten/ally	  increase	  the	  es/mated	  errors).	  
Summary	  


Reaching Errors Under G-Loading (and Vibration)

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