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RSDK-2401 move to position calls with particular start goal specifications will erroneously fail #2153

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merged 3 commits into from
Apr 4, 2023
Merged

RSDK-2401 move to position calls with particular start goal specifications will erroneously fail #2153

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cc1e0e0
Fix cbirrt extending tree with near-identical configurations
biotinker Apr 3, 2023
a71ef0f
Update qstep to escape from configurations which gradient descend to …
biotinker Apr 3, 2023
378f5e0
Fix data race
biotinker Apr 4, 2023
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31 changes: 25 additions & 6 deletions motionplan/cBiRRT.go
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Original file line number Diff line number Diff line change
Expand Up @@ -269,12 +269,17 @@ func (mp *cBiRRTMotionPlanner) constrainedExtend(
near, target node,
mchan chan node,
) {
// Once per extend, allow qstep to be doubled as a means to escape from configurations which gradient descend to their seed
qstep := mp.algOpts.qstep
doubled := false

oldNear := near
// This should iterate until one of the following conditions:
// 1) we have reached the target
// 2) the request is cancelled/times out
// 3) we are no longer approaching the target and our "best" node is further away than the previous best
// 4) further iterations change our best node by close-to-zero amounts
// 5) we have iterated more than maxExtendIter times
for i := 0; i < maxExtendIter; i++ {
select {
case <-ctx.Done():
Expand All @@ -285,18 +290,13 @@ func (mp *cBiRRTMotionPlanner) constrainedExtend(

dist := mp.planOpts.DistanceFunc(&Segment{StartConfiguration: near.Q(), EndConfiguration: target.Q()})
oldDist := mp.planOpts.DistanceFunc(&Segment{StartConfiguration: oldNear.Q(), EndConfiguration: target.Q()})
nearDist := mp.planOpts.DistanceFunc(&Segment{StartConfiguration: near.Q(), EndConfiguration: oldNear.Q()})
switch {
case dist < mp.algOpts.JointSolveDist:
mchan <- near
return
case dist > oldDist:
mchan <- oldNear
return
case i > 2 && nearDist < math.Pow(mp.algOpts.JointSolveDist, 3):
// not moving enough to make meaningful progress. Do not trigger on first iteration.
mchan <- oldNear
return
}

oldNear = near
Expand All @@ -309,7 +309,7 @@ func (mp *cBiRRTMotionPlanner) constrainedExtend(
newNear = append(newNear, nearInput)
} else {
v1, v2 := nearInput.Value, target.Q()[j].Value
newVal := math.Min(mp.algOpts.qstep[j], math.Abs(v2-v1))
newVal := math.Min(qstep[j], math.Abs(v2-v1))
// get correct sign
newVal *= (v2 - v1) / math.Abs(v2-v1)
newNear = append(newNear, referenceframe.Input{nearInput.Value + newVal})
Expand All @@ -319,6 +319,25 @@ func (mp *cBiRRTMotionPlanner) constrainedExtend(
newNear = mp.constrainNear(ctx, randseed, oldNear.Q(), newNear)

if newNear != nil {
nearDist := mp.planOpts.DistanceFunc(&Segment{StartConfiguration: oldNear.Q(), EndConfiguration: newNear})
if nearDist < math.Pow(mp.algOpts.JointSolveDist, 3) {
if !doubled {
doubled = true
// Check if doubling qstep will allow escape from the identical configuration
// If not, we terminate and return.
// If so, qstep will be reset to its original value after the rescue.
for i, q := range qstep {
qstep[i] = q * 2.0
}
continue
} else {
// We've arrived back at very nearly the same configuration again; stop solving and send back oldNear.
// Do not add the near-identical configuration to the RRT map
mchan <- oldNear
return
}
}
qstep = mp.algOpts.qstep
// constrainNear will ensure path between oldNear and newNear satisfies constraints along the way
near = &basicNode{q: newNear}
rrtMap[near] = oldNear
Expand Down