# Copyright 2020 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
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"""deluca.agents._pid"""
from numbers import Real
from typing import Sequence
import jax.numpy as jnp
from deluca.agents.core import Agent
DEFAULT_K = [3.0, 4.0, 0.0]
[docs]class PID(Agent):
"""
PID: agent that plays a PID policy
Todo:
- Allow for variable time deltas
"""
[docs] def __init__(self, K: Sequence[int] = None, RC: Real = 0.5, dt: Real = 0.03, **kwargs) -> None:
"""
Description: initializes the PID agent
Args:
K (Sequence[int]): sequence of PID parameters
RC (Real): decay parameter
dt (Real): time increment
Returns:
None
"""
if not isinstance(K, Sequence) or len(K) != 3 or not all(isinstance(x, Real) for x in K):
self.throw(ValueError, "K must be a list or tuple of 3 real numbers, P, I, and D")
# controller coefficients
self.K_P, self.K_I, self.K_D = K or DEFAULT_K
# controller states
self.P, self.I, self.D = 0.0, 0.0, 0.0
self.RC = RC
self.dt = dt
[docs] def __call__(self, state: jnp.ndarray) -> jnp.ndarray:
"""
Description: provide an action given a state
Args:
state (jnp.ndarray): the error PID must compensate for
Returns:
jnp.ndarray: action to take
"""
decay = self.dt / (self.dt + self.RC)
self.I += decay * (state - self.I)
self.D += decay * (state - self.P - self.D)
self.P = state
return self.K_P * self.P + self.K_I * self.I + self.K_D * self.D