A collision risk assessment method in dynamic environment

Abstract

The present invention discloses a collision risk assessment method in a dynamic environment. Unlike most collision risk assessment methods, this method is based on the premise that the autonomous equipment tracks the expected trajectory. Based on the geometric and motion information of the autonomous equipment and the obstacle, as well as the safe distance that should be maintained between them, the speed barrier of the obstacle in the relative speed space of the autonomous equipment relative to the obstacle is calculated. Based on this, the conditions under which the obstacle needs to be avoided and the conditions under which the obstacle is deemed to have been avoided are proposed, and the status of the obstacle is marked as active or inactive to facilitate the overall collision avoidance decision of the autonomous equipment.

Description

Technical Field

[0001] The invention relates to a collision risk assessment method in a dynamic environment. Background Art

[0002] Velocity Obstacle (VO): This method generates a cone-shaped obstacle in velocity space (hence the name velocity barrier) that guarantees that no future collisions will occur as long as the autonomous vehicle’s velocity vector is outside the VO.

[0003] from Start to The auxiliary rays of the direction are expressed as:

[0004] Given an autonomous device of shape A with a speed Move, given an obstacle of shape B with speed Moving, the safe distance between the autonomous equipment boundary and the obstacle boundary is d and Then the danger zone of B is

[0005] Minkowski and:

[0006] Mirror Image:

[0007] Obstacle expansion: When A is simplified to a point, the danger zone of B relative to A is

[0008] Therefore, VO of B in the velocity space of A is

[0009] B's VO in the relative velocity space of A relative to B is like Figure 1 Shown is a schematic diagram of obstacle expansion and speed barrier.

[0010] Most current collision risk assessment methods can only predict whether an autonomous vehicle will collide with an obstacle based on the geometric and motion information of the autonomous vehicle and the obstacle at its current speed. They do not consider the safe distance that should be maintained between the autonomous vehicle and the obstacle, which cannot ensure the safety of the autonomous vehicle when encountering uncertain emergencies. Moreover, most current collision risk assessment methods only propose the conditions under which a detected obstacle needs to be avoided, without mentioning the conditions under which the obstacle is considered avoided. This can affect the autonomous vehicle's overall collision avoidance decision-making when it needs to avoid multiple dynamic and static obstacles simultaneously, thereby reducing its collision avoidance performance. Summary of the Invention

[0011] To address the problems existing in the above-mentioned prior art, the present invention proposes a collision risk assessment method in a dynamic environment. When an autonomous device detects an obstacle while tracking a desired trajectory, it calculates the speed barrier of the obstacle in the relative speed space of the autonomous device relative to itself based on the geometric and motion information of the autonomous device and the obstacle, as well as the safe distance that should be maintained between them. Based on this, the present invention proposes the conditions under which the obstacle needs to be avoided and the conditions under which the obstacle is deemed to have been avoided.

[0012] The present invention can be implemented through the following technical solutions:

[0013] A collision risk assessment method in a dynamic environment comprises the following steps:

[0014] 1) Project the detected obstacles into velocity space and expand to form VO o ;

[0015] 2) The initial state of the obstacle is inactive;

[0016] 3) Determine the expected relative speed of the autonomous device relative to the obstacle Is it in VO O If yes, calculate the collision avoidance reaction time t d , determine the actual relative speed of the autonomous equipment relative to the obstacle Is it in VO O If yes, calculate the collision avoidance reaction time t0;

[0017] 4) Determine whether the obstacle meets the conditions that need to be avoided. If so, calculate the position vector of the actual position of the autonomous device relative to its expected position at this time And update the state of the obstacle to active, otherwise the obstacle remains in the current inactive state;

[0018] 5) End the current moment;

[0019] 6) Enter the next moment and calculate VO o ;

[0020] 7) If the current state of the obstacle is inactive, return to step 3); if the current state of the obstacle is active, calculate the variable b;

[0021] 8) Determine whether the obstacle meets the conditions for being avoided. If so, update the state of the obstacle to inactive; otherwise, the obstacle maintains its current active state;

[0022] 9) Return to step 5).

[0023] Furthermore, the conditions under which the obstacle needs to be avoided in step 4) are specifically:

[0024] Only when or When the autonomous equipment is in danger of colliding with an obstacle, a time threshold t is set. r To evaluate the collision risk, assume that at this time, The closest intersection point with the inflated obstacle is Collision avoidance reaction time The closest intersection point with the inflated obstacle is Collision avoidance reaction time An inactive barrier becomes active when one of the following conditions is met:

[0025] 1) And t d ≤t r

[0026] 2) And t0≤t r .

[0027] Furthermore, the variable b is defined as:

[0028]

[0029] Among them, the current expected position of the autonomous equipment is and the actual location is At any moment, the position vector of the actual position of the autonomous device relative to its desired position is expressed as Among them, when the obstacle is just activated, the position vector of the actual position of the autonomous equipment relative to its expected position is expressed as Define the starting point as And the direction is The same auxiliary ray is

[0030] When b=-1, the actual position of the autonomous device is within the auxiliary ray on the left side;

[0031] When b=1, the actual position of the autonomous device is within the auxiliary ray the right side;

[0032] When b=0, the actual position of the autonomous device is within the auxiliary ray superior.

[0033] Furthermore, the conditions for determining that the obstacle has been avoided in step 8) are as follows: let b0 be the value of b at the previous moment, and when one of the following conditions is met, the obstacle in the active state is marked as inactive:

[0034] 1) And b=0;

[0035] 2) And b*b0<0.

[0036] Beneficial effects

[0037] The present invention aims to apply a proposed collision risk assessment method to an autonomous device, when it detects a dynamic or static obstacle while tracking a desired trajectory. This method uses the geometric and motion information of the autonomous device and the obstacle, as well as the safe distance that should be maintained between them, to calculate the obstacle's speed barrier in the autonomous device's relative velocity space relative to the autonomous device. The proposed collision risk assessment method then marks the obstacle's status as active or inactive based on the proposed conditions for obstacle avoidance and the conditions for obstacle avoidance. This facilitates the autonomous device's overall collision avoidance decision-making, specifically requiring the autonomous device to avoid only activated obstacles. The proposed collision risk assessment method assesses the obstacle's speed barrier in the autonomous device's relative velocity space relative to the autonomous device, providing an early warning and preventing collisions caused by insufficient reaction time or safe distance upon detecting a dangerous obstacle. Furthermore, the proposed conditions for obstacle avoidance facilitate the autonomous device's overall collision avoidance decision-making when it needs to simultaneously avoid multiple dynamic and static obstacles, thereby improving its collision avoidance performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of obstacle expansion and speed barrier in background technology;

[0039] Figure 2 The expected relative speed and actual relative speed of the autonomous equipment relative to the obstacle are in VO O Internal schematic diagram;

[0040] Figure 3-1 The process of autonomous equipment deviating from its desired trajectory to avoid obstacles;

[0041] Figure 3-2 The actual position of the autonomous device in the auxiliary ray the right side;

[0042] Figure 4 This is a flow chart of the collision risk assessment method. DETAILED DESCRIPTION

[0043] The following describes the embodiments of the present invention through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0044] Some obstacles detected by the autonomous system are likely to collide with the autonomous system soon and are therefore set to active. However, obstacles that pose no risk of collision are set to inactive. For activated obstacles, the autonomous system should take measures to avoid collision. It is assumed that all detected obstacles are initially inactive. Generally speaking, the autonomous system's collision avoidance strategy is determined by information from all activated obstacles. Once some activated obstacles have been avoided by the autonomous system, their status should be restored to inactive; otherwise, the autonomous system's overall collision avoidance decision will be affected.

[0045] Represents a vector The symbol '\' represents the remainder. Represents a vector The expected speed and actual speed of the autonomous equipment are and The speed of the obstacle is The desired relative speed of the autonomous vehicle relative to the obstacle The actual relative speed of the autonomous device relative to the obstacle The conditions for obstacles to be avoided and the conditions for obstacles to be considered avoided are set as follows:

[0046] 1. Conditions under which obstacles need to be avoided.

[0047] Only when or When the autonomous device is in danger of colliding with an obstacle, it is necessary to calculate how long it will take for a collision to occur. If the time is long, it means that the autonomous device is relatively safe and there is no need to take collision avoidance measures. Therefore, a time threshold t is needed. r To evaluate the collision risk. Assume that at this time, The closest intersection point with the inflated obstacle is Collision avoidance reaction time The closest intersection point with the inflated obstacle is Collision avoidance reaction time An inactive barrier becomes active when one of the following conditions is met:

[0048] 1) And t d ≤t r ;

[0049] 2) And t0≤t r ;like Figure 2The expected relative speed and actual relative speed of the autonomous equipment relative to the obstacle are shown in VO O Inside.

[0050] 2. Conditions under which an obstacle is deemed to have been avoided.

[0051] Whether the activated obstacle has been avoided depends on VO O 、 and the current desired position of autonomous equipment and actual location At any moment, the position vector of the autonomous device’s actual position relative to its desired position is expressed as Among them, when the obstacle is just activated, the position vector of the actual position of the autonomous equipment relative to its expected position is expressed as Define the starting point as And the direction is The same auxiliary ray is

[0052] When the autonomous device avoids an obstacle, it will go around it from the left or right side of the obstacle. In other words, the autonomous device and the auxiliary ray The distance between them will generally increase first, then gradually decrease until it reaches zero. Define the variable b as follows:

[0053]

[0054] When b = -1, it means that the actual position of the autonomous equipment is within the auxiliary ray on the left side;

[0055] When b=1, it means that the actual position of the autonomous equipment is within the auxiliary ray the right side;

[0056] When b = 0, it means that the actual position of the autonomous equipment is within the auxiliary ray superior.

[0057] b0 is the value of b at the previous moment. An active barrier is marked as inactive when one of the following conditions is met:

[0058] 1) And b=0;

[0059] 2) And b*b0<0; if Figure 3-1 Schematic diagram of the process of autonomous equipment deviating from the desired trajectory to avoid obstacles; Figure 3-2 The actual position of the autonomous device in the auxiliary ray Schematic diagram on the right side.

[0060] The flowchart of the collision risk assessment method under dynamic environment of the present invention is as follows: Figure 4 The specific steps are as follows:

[0061] 1) Project the detected obstacles into velocity space and expand to form VO O .

[0062] 2) The initial state of the obstacle is inactive.

[0063] 3) Determine the expected relative speed of the autonomous device relative to the obstacle Is it in VO O If yes, calculate the collision avoidance reaction time t d Determine the actual relative speed of the autonomous equipment relative to the obstacle Is it in VO O If yes, calculate the collision avoidance reaction time t0.

[0064] 4) Determine whether the obstacle meets the conditions that need to be avoided. If so, calculate the position vector of the actual position of the autonomous device relative to its expected position at this time The state of the obstacle is updated to active, otherwise the obstacle remains in its current inactive state.

[0065] 5) End the current moment;

[0066] 6) Enter the next moment and calculate VO O ;

[0067] 7) If the obstacle is currently inactive, return to step 3). If the obstacle is currently active, calculate variable b.

[0068] 8) Determine whether the obstacle meets the conditions for being avoided. If so, update the state of the obstacle to inactive; otherwise, the obstacle maintains its current active state;

[0069] 9) Return to step 5).

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A collision risk assessment method in a dynamic environment, characterized in that: The following steps are involved: 1) Project the detected obstacles into velocity space and expand to form VO O ; 2) The initial state of the obstacle is inactive; 3) Determine the expected relative speed of the autonomous device relative to the obstacle Is it in VO O If yes, calculate the collision avoidance reaction time t d , determine the actual relative speed of the autonomous equipment relative to the obstacle Is it in VO O If yes, calculate the collision avoidance reaction time t0; 4) Determine whether the obstacle meets the conditions that need to be avoided. If so, calculate the position vector of the actual position of the autonomous device relative to its expected position at this time And update the state of the obstacle to active, otherwise the obstacle remains in the current inactive state; 5) End the current moment; 6) Enter the next moment and calculate VO O ; 7) If the current state of the obstacle is inactive, return to step 3); if the current state of the obstacle is active, calculate the variable b; 8) Determine whether the obstacle meets the conditions for being avoided. If so, update the state of the obstacle to inactive; otherwise, the obstacle maintains its current active state; 9) Return to step 5); The conditions under which obstacles need to be avoided in step 4) are specifically: Only when or When the autonomous equipment is in danger of colliding with an obstacle, a time threshold t is set. r To evaluate the collision risk, assume that at this time, The closest intersection point with the inflated obstacle is Collision avoidance reaction time The closest intersection point with the inflated obstacle is Collision avoidance reaction time An inactive barrier becomes active when one of the following conditions is met: 1) And t d ≤t r 2) And t0≤t r ; The conditions for determining that an obstacle has been avoided in step 8) are as follows: let b0 be the value of b at the previous moment, and when one of the following conditions is met, the obstacle in the active state is marked as inactive: 1) And b=0; 2) And b*b0<0; The variable b is defined as: Among them, the current expected position of the autonomous equipment is and the actual location is At any moment, the position vector of the actual position of the autonomous device relative to its desired position is expressed as Among them, when the obstacle is just activated, the position vector of the actual position of the autonomous equipment relative to its expected position is expressed as Define the starting point as And the direction is The same auxiliary ray is When b=-1, the actual position of the autonomous device is within the auxiliary ray on the left side; When b=1, the actual position of the autonomous device is within the auxiliary ray the right side; When b=0, the actual position of the autonomous device is within the auxiliary ray superior.

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