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still not running, but a lot further along

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This commit is contained in:
Simen Svale Skogsrud
2011-01-22 23:29:02 +01:00
parent c9df285604
commit 4103e6ca00
8 changed files with 142 additions and 93 deletions
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111
stepper_plan.c
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@@ -26,50 +26,73 @@
#include "nuts_bolts.h"
#include "stepper.h"
#include "config.h"
#include "wiring_serial.h"
struct Block block_buffer[BLOCK_BUFFER_SIZE]; // A ring buffer for motion instructions
volatile int block_buffer_head; // Index of the next block to be pushed
volatile int block_buffer_tail; // Index of the block to process now
uint8_t acceleration_management; // Acceleration management active?
inline uint32_t estimate_acceleration_distance(int32_t current_rate, int32_t target_rate, int32_t acceleration) {
return((target_rate*target_rate-current_rate*current_rate)/(2*acceleration));
// The distance it takes to accelerate from initial_rate to target_rate using the given acceleration
inline double estimate_acceleration_distance(double initial_rate, double target_rate, double acceleration) {
return((target_rate*target_rate-initial_rate*initial_rate)/(2L*acceleration));
}
inline uint32_t estimate_acceleration_ticks(int32_t start_rate, int32_t acceleration_per_tick, int32_t step_events) {
return(
round(
(sqrt(2*acceleration_per_tick*step_events+(start_rate*start_rate))-start_rate)/
acceleration_per_tick));
// This function gives you the point at which you must start braking (at the rate of -acceleration) if
// you started at speed initial_rate and accelerated until this point and want to end at the final_rate after
// a total travel of distance. This can be used to compute the intersection point between acceleration and
// deceleration in the cases where the trapezoid has no plateau (i.e. never reaches maximum speed)
/*
+ <- some rate that must be < maximum allowable rate
/|\
/ | \
/ | + <- final_rate
/ | |
initial_rate -> +----+--+
0 ^ ^
| |
result distance
*/
inline double intersection_distance(double initial_rate, double final_rate, double acceleration, double distance) {
return((2*acceleration*distance-initial_rate*initial_rate+final_rate*final_rate)/(4*acceleration));
}
// See bottom of this module for a comment outlining the reasoning behind the mathematics behind the
// preceding functions.
// Calculates trapezoid parameters so that the entry- and exit-speed is compensated by the provided factors.
// In practice both factors must be in the range 0 ... 1.0
void calculate_trapezoid_for_block(struct Block *block, double entry_factor, double exit_factor) {
block->initial_rate = round(block->nominal_rate*entry_factor);
int32_t final_rate = round(block->nominal_rate*entry_factor);
int32_t acceleration_per_second = block->rate_delta*ACCELERATION_TICKS_PER_SECOND;
int32_t acceleration_steps =
estimate_acceleration_distance(block->initial_rate, block->nominal_rate, acceleration_per_second);
int32_t decelleration_steps =
int32_t accelerate_steps =
round(estimate_acceleration_distance(block->initial_rate, block->nominal_rate, acceleration_per_second));
int32_t decelerate_steps =
estimate_acceleration_distance(block->nominal_rate, final_rate, -acceleration_per_second);
printString("ir="); printInteger(block->initial_rate); printString("\n\r");
printString("nr="); printInteger(block->nominal_rate); printString("\n\r");
printString("rd="); printInteger(block->rate_delta); printString("\n\r");
printString("aps="); printInteger(acceleration_per_second); printString("\n\r");
printString("acs="); printInteger(accelerate_steps); printString("\n\r");
printString("dcs="); printInteger(decelerate_steps); printString("\n\r");
printString("ts="); printInteger(block->step_event_count); printString("\n\r");
// Check if the acceleration and decelleration periods overlap. In that case nominal_speed will
// never be reached but that's okay. Just truncate both periods proportionally so that they
// fit within the allotted step events.
int32_t plateau_steps = block->step_event_count-acceleration_steps-decelleration_steps;
if (plateau_steps < 0) {
int32_t half_overlap_region = fabs(plateau_steps)/2;
int32_t plateau_steps = block->step_event_count-accelerate_steps-decelerate_steps;
if (plateau_steps < 0) {
accelerate_steps = round(
intersection_distance(block->initial_rate, final_rate, acceleration_per_second, block->step_event_count));
plateau_steps = 0;
acceleration_steps = max(acceleration_steps-half_overlap_region,0);
decelleration_steps = max(decelleration_steps-half_overlap_region,0);
}
block->accelerate_ticks = estimate_acceleration_ticks(block->initial_rate, block->rate_delta, acceleration_steps);
if (plateau_steps) {
block->plateau_ticks = round(1.0*plateau_steps/(block->nominal_rate*ACCELERATION_TICKS_PER_SECOND));
} else {
block->plateau_ticks = 0;
}
}
printString("No plateau, so: acs="); printInteger(accelerate_steps); printString("\n\r");
}
block->accelerate_until = accelerate_steps;
block->decelerate_after = accelerate_steps+plateau_steps;
}
inline double estimate_max_speed(double max_acceleration, double target_velocity, double distance) {
return(sqrt(-2*max_acceleration*distance+target_velocity*target_velocity));
@@ -185,15 +208,17 @@ void plan_buffer_line(int32_t steps_x, int32_t steps_y, int32_t steps_z, uint32_
// axes might step for every step event. Travel per step event is then sqrt(travel_x^2+travel_y^2).
// To generate trapezoids with contant acceleration between blocks the rate_delta must be computed
// specifically for each line to compensate for this phenomenon:
double travel_per_step = (1.0*millimeters)/block->step_event_count;
double travel_per_step = millimeters/block->step_event_count;
printString("travel_per_step*10000=");
printInteger(travel_per_step*10000);printString("\n\r");
block->rate_delta = round(
(settings.acceleration/(60.0*ACCELERATION_TICKS_PER_SECOND))/ // acceleration mm/min per acceleration_tick
((settings.acceleration*60.0)/(ACCELERATION_TICKS_PER_SECOND))/ // acceleration mm/sec/sec per acceleration_tick
travel_per_step); // convert to: acceleration steps/min/acceleration_tick
if (acceleration_management) {
calculate_trapezoid_for_block(block,0,0); // compute a conservative acceleration trapezoid for now
} else {
block->accelerate_ticks = 0;
block->plateau_ticks = 0;
block->accelerate_until = 0;
block->decelerate_after = 0;
block->rate_delta = 0;
}
@@ -206,3 +231,35 @@ void plan_buffer_line(int32_t steps_x, int32_t steps_y, int32_t steps_z, uint32_
block_buffer_head = next_buffer_head;
}
/*
Mathematica reasoning behind the mathematics in this module:
s == speed, a == acceleration, t == time, d == distance
Basic definitions:
Speed[s_, a_, t_] := s + (a*t)
Travel[s_, a_, t_] := Integrate[Speed[s, a, t], t]
Distance to reach a specific speed with a constant acceleration:
Solve[{Speed[s, a, t] == m, Travel[s, a, t] == d}, d, t]
d -> (m^2 - s^2)/(2 a) --> estimate_acceleration_distance()
Speed after a given distance of travel with constant acceleration:
Solve[{Speed[s, a, t] == m, Travel[s, a, t] == d}, m, t]
m -> Sqrt[2 a d + s^2]
DestinationSpeed[s_, a_, d_] := Sqrt[2 a d + s^2]
When to start braking (di) to reach a specified destionation speed (s2) after accelerating
from initial speed s1 without ever stopping at a plateau:
Solve[{DestinationSpeed[s1, a, di] == DestinationSpeed[s2, a, d - di]}, di]
di -> (2 a d - s1^2 + s2^2)/(4 a) --> intersection_distance()
IntersectionDistance[s1_, s2_, a_, d_] := (2 a d - s1^2 + s2^2)/(4 a)
*/