README.md 3.29 KB
Newer Older
1
# LabProcesses
Fredrik Bagge Carlson's avatar
Fredrik Bagge Carlson committed
2
3
4
5
6
7
8
9
10
11
This package contains an (programming- as well as connection-) interface to serve
as a base for the implementation of lab-process software. The first exampel of
an implementaiton of this interface is for the ball-and-beam process, which is
used in Lab1 FRTN35: frequency response analysis of the beam. The lab is implemented
in [BallAndBeam.jl](https://gitlab.control.lth.se/processes/BallAndBeam.jl), a
package that makes use of `LabProcesses.jl` to handle the communication with
the lab process and/or a simulated version thereof. This way, the code written
for frequency response analysis of the beam can be run on another process
implementing the same interface (or a simulated version) by changeing a single
line of code :)
12

Fredrik Bagge Carlson's avatar
Fredrik Bagge Carlson committed
13
14
15
16
17
18
19
20
21
22
## Installation
1. Start julia
2. Install LabProcesses.jl using command Pkg.clone("https://gitlab.control.lth.se/processes/LabProcesses.jl.git") Lots of packages will now be installed, this will take some time.

## How to implement a new process
1. Locate the file [interface.jl](https://gitlab.control.lth.se/processes/LabProcesses.jl/blob/master/src/interface.jl)
2. Copy all function definitions.
3. Create a new file under `/interface_implementations` where you paste all the
copied definitions and implement them. See [`/interface_implementations/ballandbeam.jl`](https://gitlab.control.lth.se/processes/LabProcesses.jl/blob/master/src/interface_implementations/ballandbeam.jl) for an example.
4. Above all function implementations you must define the process type, e.g,
Fredrik Bagge Carlson's avatar
Fredrik Bagge Carlson committed
23
24
25
26
27
28
    ```julia
    struct BallAndBeam <: PhysicalProcess
        h::Float64
    end
    BallAndBeam() = BallAndBeam(0.01) # Constructor with default value of sample time
    ```
Fredrik Bagge Carlson's avatar
Fredrik Bagge Carlson committed
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
Make sure you inherit from `PhysicalProcess` or `SimulatedProcess` as appropriate.
5. Documentation of all interface functions is available in the file [interface_documentation.jl](https://gitlab.control.lth.se/processes/LabProcesses.jl/blob/master/src/interface_documentation.jl)

## Control a process
The interface `AbstractProcess` defines the functions `control(P, u)` and `measure(P)`.
These functions can be used to implement your own control loops. A common loop
with a feedback controller and a feedforward filter on the reference is implemented
in the function [`run_control_2DOF`](@ref).

The macro `@periodically` might come in handy if you want to implement your own loop.
Consider the following example, in which the loop body will be run periodically
with a sample time of `h` seconds.
```julia
for (i,t) = enumerate(0:h:duration)
    @periodically h begin
        y[i]       = measure(P)
        r[i]       = reference(t)
        u[i]       = control(i)
        control(P, u[i])
    end
end
```

Often one finds the need to implement a stateful controller, i.e., a function
that has a memory or state. To this end, the function [`sysfilter`](@ref) is
Fredrik Bagge Carlson's avatar
Fredrik Bagge Carlson committed
54
55
provided. This function is used to implement control loops where a signal is filtered through a
dynamical system, i.e., `U(z) = C(z)E(z)`. Usage is demonstrated below
Fredrik Bagge Carlson's avatar
Fredrik Bagge Carlson committed
56
57
58
59
```julia
stateC = init_sysfilter(C)
function control(i)
    e  = r[i]-y[i]
Fredrik Bagge Carlson's avatar
Fredrik Bagge Carlson committed
60
    u  = sysfilter!(stateC, C, e)
Fredrik Bagge Carlson's avatar
Fredrik Bagge Carlson committed
61
62
63
64
end
```
`C` must here be represented by a [`StateSpace`](@ref) type from [`ControlSystems.jl`](https://github.com/JuliaControl/ControlSystems.jl).
`TransferFunction` types can easily be converted to a `StateSpace` by `Gss = ss(Gtf)`.