Method for the open-loop and closed-loop control of a device including a movement module during the interaction of the device with a human, and device controlled in such a manner
A method for open-loop and closed-loop control of a device having a movement module, in terms of its interaction with a human, is based on an energy-based control process that makes it possible to monitor the amount of an overall energy in the system including the device and the human in dependence on a measured control variable describing the speed at which the device or its movement module moves. The method considers the entire power cycle, in particular the dynamics of the energy or power flow, in the system including the device and the human and takes into account the performance of the human during the closed-loop control. The method also enables the participation state of the human who is using the device to be determined in an iterative learning process without additional sensors. A device for carrying out the method is also provided.
1 . A method for open-loop and closed-loop control of a device, at least including a movement module, in terms of an interaction of the device with a human, the method comprising:
defining an energy network formed at least of:
a first power component describing an amount of energy per unit time supplied by the device to an overall energy of a system of the device and the human;
a second power component describing an amount of energy per unit time lost by the device by way of internal open-loop and closed-loop control processes outside of work to be carried out primarily aided by the movement module; and
a third power component describing an amount of energy per unit time supplied by the human to the overall energy;
defining the overall energy of the energy network of the system of the device and the human as a controlled variable;
defining a speed with which the device interacts with the human by way of the movement module as a control variable, with the movement module intended to traverse a desired trajectory;
causing the overall energy of the energy network to:
increase as more movement independently carried out by the human deviates from a movement along the trajectory initially specified by the device; and
decrease again as the movement independently carried out by the human approaches the movement along the trajectory initially specified by the device;
determining the overall energy of the energy network during the movement of the movement module, and
varying the control variable during the movement of the movement module,
depending on the determined overall energy, causing the overall energy to:
remain in an interval of S≤Smax−SΔ when located in the interval, or
approach the interval S≤Smax−SΔ again when located in an interval of S>Smax−SΔ, where:
Smax=a chosen upper boundary of the overall energy; and
SΔ=Smax−Sx1, where Sx1 represents individual values of the controlled variable or the overall energy S and x=n is used to designate values in an interval with Pin>0 and x=p is used to designate values in an interval with Pin<0.
2 . The method according to claim 1 , which further comprises:
using the device as a rehabilitation mechanism configured for a rehabilitation of at least joints, muscles and tendons of lower extremities of a human according to plan;
bringing the movement module into an operative connection with the lower extremities of the human; and
providing the movement module with:
at least one force sensor for measuring an absolute value of a force between the movement module and the lower extremity of the human, and
at least one angle sensor for measuring a direction of the force between the movement module and the lower extremity of the human.
3 . The method according to claim 1 , which further comprises defining the control variable as:
Ω
=
{
γ
p
i
f
S
max
S
Λ
P
in
<
0
1
+
y
p
-
1
2
[
1
+
cos
(
S
max
-
S
S
Δ
π
)
]
i
f
S
max
-
S
Δ
<
S
<
S
max
Λ
P
in
<
0
1
i
f
S
≤
S
max
-
S
Δ
1
+
y
n
+
1
2
[
1
+
cos
(
S
max
-
S
S
Δ
π
)
]
i
f
S
max
-
S
Δ
<
S
<
S
max
Λ
P
in
>
0
-
γ
n
i
f
S
max
≤
S
Λ
P
in
>
0
where:
γ p =maximum permitted positive value for the control variable;
γ n =maximum permitted negative value or absolute value for the control variable;
S=overall energy of the system of the device and the human;
S max =chosen upper boundary of the overall energy; and
SΔ=S max −S p_x , where S p_x represents individual values of the controlled variable S.
4 . The method according to claim 1 , which further comprises defining the control variable as:
Ω
=
{
γ
p
i
f
S
max
S
Λ
P
in
<
0
1
+
γ
p
-
1
2
[
1
+
cos
(
S
max
-
S
S
Δ
π
)
]
i
f
S
max
-
S
Δ
<
S
<
S
max
Λ
P
in
<
0
1
i
f
S
≤
S
max
-
S
Δ
{
1
+
1
2
[
1
+
cos
(
S
max
-
S
Δ
+
S
Δ
-
S
δ
2
-
S
S
Δ
-
S
δ
2
π
)
]
0
1
+
1
2
[
1
+
cos
(
S
max
-
S
S
Δ
-
S
δ
2
π
)
]
i
f
S
max
-
S
Δ
<
S
<
S
max
-
S
Δ
+
S
Δ
-
S
δ
2
Λ
P
in
>
0
i
f
S
max
-
S
Δ
+
s
Δ
-
S
δ
2
<
S
<
S
max
-
S
Δ
-
S
δ
2
Λ
P
in
>
0
i
f
S
max
-
S
Δ
-
S
δ
2
<
S
<
S
max
Λ
P
in
>
0
-
γ
n
i
f
S
max
≤
S
Λ
P
in
>
0
where:
γ p =maximum permitted positive value for the control variable;
γ n =maximum permitted negative value or absolute value for the control variable;
S=overall energy of the system of the device and the human;
S max =chosen upper boundary of the overall energy;
SΔ=S max −S p_x , where S p_x represents individual values of the controlled variable S; and
Sδ=region in the middle of SΔ for which the control variable is set equal to zero, where P in >0.
5 . The method according to claim 1 , which further comprises defining the control variable as:
Ω
=
{
γ
p
i
f
S
max
·
ζ
≤
S
Λ
P
in
<
0
1
+
y
p
-
1
2
[
1
+
cos
(
S
max
·
ζ
-
S
S
Δ
π
)
]
i
f
S
max
·
ζ
-
S
Δ
<
S
<
S
max
·
ζΛ
P
in
<
0
1
i
f
S
≤
S
max
·
ζ
-
S
Δ
1
+
y
n
+
1
2
[
1
+
cos
(
S
max
·
ζ
-
S
S
Δ
π
)
]
i
f
S
max
·
ζ
-
S
Δ
<
S
<
S
max
·
ζΛ
P
in
>
0
-
γ
n
i
f
S
max
·
ζ
≤
S
Λ
P
in
>
0
where:
γ p =maximum permitted positive value for the control variable;
γ n =maximum permitted negative value or absolute value for the control variable;
S=overall energy of the system of the device and the human;
S max =chosen upper boundary of the overall energy;
SΔ=S max ·ζ−S p_x , where S p_x represents individual values of the controlled variable S;
ζ
=
{
1
if
t
_
<
τ
ϱ
t
_
<
τ
for
all
other
values
of
t
_
where
t =time during which the device ( 1 ) is at a standstill;
τ=maximum time the device ( 1 ) is permitted to be at a standstill.
6 . The method according to claim 1 , which further comprises damping the variation of the control variable during the movement of the movement module based on the determined overall energy or by implementing at least one of a filter, a rate restriction or a limitation of an absolute value of a first derivative of the control variable with respect to the overall energy.
7 . The method according to claim 1 , which further comprises:
defining the overall energy of the system of the device and the human, or including a virtual absolute energy value and an actual absolute energy value, as an overall storage function S=S ce or as an overall storage function S=S ce +S ee ; and
defining the energy storage function of the control deviation as:
S
ee
=
1
2
x
~
.
T
M
C
(
q
)
x
~
.
+
1
2
x
~
T
K
x
x
~
.
where:
S ce =control error energy storage function;
M C (q)=the Cartesian moment of inertia matrix;
K x =the Cartesian stiffness matrix; and
S ee =overall energy of an end effector of the device or of the movement module formed of kinetic and potential energy.
8 . The method according to claim 7 , which further comprises:
determining the energy storage function by way of the first power component, and combining the first power component by calculation with the second power component; or
calculating the energy storage function by way of an interaction force between the device and the human, or measuring the energy storage function by using a force sensor for measuring an absolute value of a force between the movement module and the lower extremity of the human.
9 . The method according to claim 7 , which further comprises determining a time derivative of the overall storage function as {dot over (S)}=P in +P h −P diss , where:
P in ∈R=power input into the system generated by a movement generator;
P diss ∈R=power lost by control damping; and
P h =power supplied to the system of the device and the human by the human.
10 . The method according to claim 1 , which further comprises determining a limit to be chosen for carrying out a movement by way of an iterative learning process by the device while the movement is carried out, the limit being for at least one of the overall storage function corresponding to the overall energy or a variable SΔ=S max −S p_x , where S p_x are individual values of the overall energy; and
changing at least one of a learning factor or a forgetting factor for determining a participation state of the human in the movement specified by the device over time, or changing linearly over time, within a scope of the iterative learning process until at least one of the learning factor or the forgetting factor has reached a final value defined in advance.
11 . The method according to claim 10 , which further comprises:
choosing a value for the limit in a first iteration step, when the device fully assists the human with carrying out the movement and the control variable has a value of 1;
reducing the value of the limit in each further iteration step for as long as the control variable maintains the value of 1; and
when the control variable deviates from the value of 1, increasing the value of the limit again in a next iteration step.
12 . The method according to claim 10 , which further comprises determining an initial limit by:
initially running the device through n movement cycles without a given limit,
providing a number n of movement cycles in an interval of 2≤n≤5 movement cycles or providing 3 movement cycles;
recording an S profile;
subsequently calculating a mean value of the recorded S values as the initial limit, serving as a start value for the limit in a first iteration step of the iterative learning process in a form λ·S init with λ≥1; and
scaling at least one of the learning factor or the forgetting factor for determining a participation state of the human in the movement specified by the device based on the initial limit when initializing the iterative learning process.
13 . The method according to claim 12 , which further comprises choosing a limit for carrying out a movement, the limit being for the overall storage function corresponding to the overall energy and being split into regions based on a phase value describing a movement progress within a movement cycle of the device and determining an initial limit for each region.
14 . The method according to claim 1 , which further comprises:
choosing a limit for carrying out a movement, the limit being for the overall storage function corresponding to the overall energy, and being:
split into regions based on a phase value describing the movement progress within a movement cycle of the device,
with a region describing the phase value interval from φ str, i to φ str,i+1 , and
defining the limit to be chosen independently for each region, with the following applying to all phase values of a region:
S
max
(
ϕ
)
=
{
S
¯
max
,
i
+
S
¯
max
,
i
-
1
2
+
S
¯
max
,
i
+
S
¯
max
,
i
-
1
2
sin
(
π
ϕ
-
ϕ
str
,
i
2
Δ
)
if
ϕ
<
ϕ
str
,
i
+
Δ
S
¯
max
,
i
+
S
¯
max
,
i
-
1
2
+
S
¯
max
,
i
+
S
¯
max
,
i
+
1
2
sin
(
π
ϕ
str
,
i
+
1
-
ϕ
2
Δ
)
if
ϕ
<
ϕ
str
,
i
+
1
-
Δ
S
¯
max
,
i
for
all
other
values
of
ϕ
where Δ>0 describes a smoothing interval including a smaller value range of phase values than the regions, or a tenth of the phase values of the corresponding region; and
S max,i being a limit associated with a respective region.
15 . A device, comprising:
a rehabilitation mechanism configured for a rehabilitation of at least joints, muscles and tendons of lower extremities of a human according to plan;
a movement module configured to be brought into an operative connection with the lower extremities of the human, said the movement module including:
at least one force sensor for measuring an absolute value of a force between said movement module and the lower extremity of the human, and
at least one angle sensor for measuring a direction of the force between said movement module and the lower extremity of the human; and
a control unit configured for open-loop and closed-loop control of the device according to the method of claim 1 .