MiR logo

Test braking distance

Ensure the robots' braking distance is safe with all loads. See Test braking distance.

  • Conduct a brake test with the lightest, heaviest, and largest loads, and any loads with unusual properties.

  • Adjust the robot, the environment, or the robot payload until the stopping distance criteria in the brake test are met.

It is the responsibility of the commissioner to perform an adequate test of the robot's braking capability under the driving conditions the robot will be operating in. The brake test must be executed:

  • With maximum payload.

  • With the lightest production payload that the robot is going to operate with.

  • Within each speed interval for each Protective field.

  • At the steepest supported decline in the robot's work area.

Any hardware, footprint, or safety configuration changes must be production-ready before performing brake tests.

The commissioner must iteratively adjust the modifiable parameters and then run a brake test until the robot successfully stops in time in every test.

Dependent factors

The braking distance of the robot is particularly dependent upon the parameter in Table 3.14. If the robot fails a brake test, you must either modify a chosen parameter to reduce the distance, or you can increase the size of the robot's Protective fields to make the robot stop sooner. To change the Protective fields, see [Adjust SICK configuration file](adjusting_field sets.htm).

If you have a CE marked MiR robot, the Protective field sets are configured to comply with the safety standards of the robot. Modifications may prevent the robot from stopping in time to avoid collision with personnel and equipment. Any modifications of the SICK configuration requires a new CE certification of the robot and compliance to all safety standards listed in the specification of the application and in other way declared.

  • Do not modify the safety system without a competent third party to evaluate the safety of the design and performance of the robot after the modifications are applied.

| Parameter | Design consideration for Protective fields | | --- | --- | | Top module | Adjust the length, width, and shape of the Protective fields accordingly to match the footprint of the top module if it extends beyond the top cover of the robot. Adjust the shape of the Protective fields accordingly to create cutouts for cart or shelf legs in the view of the scanners. | | Robot speed | Speed affects the braking distance according to a quadratic relationship. For example, 2× higher speed means 4× longer braking distance. The higher the maximum speed in a monitoring case, the longer the Protective fields must be. | | Mass moment of inertia | A higher mass moment of inertia increases the braking distance when the robot pivots. The higher the mass moment of inertia, the wider the Protective fields must be. | | Payload weight | A higher payload increases the braking distance when the robot drives straight. The higher the payload, the longer the Protective fields must be. | | Payload position | When the payload's center of gravity is behind the drive wheels, it increases the braking distance when the robot drives straight. The further the center of gravity is behind the drive wheels, the longer the Protective fields must be. | | Floor surface friction | A lower friction between the wheels and floor increases the braking distance. The lower the frictional coefficient, the longer the Protective fields must be. | | Floor surface grade | When the robot is driving down a decline, it increases the braking distance. The steeper the maximum slope the robot drives down, the longer the Protective fields must be. |

Brake test method

For MiR1200 Pallet Jack, use the Brake test page in the robot interface under System > Brake test to perform a brake test. Follow the instructions in the interface to complete the test. The robot must be running MiR Fleet Enterprise software 1.2.1 or higher for the Brake test page to be available.

For deckload and hook robots, follow the instructions in the following section to perform linear and pivot brake tests.

Test setup

In order to conduct brake tests for verifying robot Protective fields, the following items are needed:

  • Robot : the robot including its top module and maximum payload.

  • Brake test area : approximately 3 m × 10 m; or the distance it takes for the robot to reach maximum speed and stop safely.

  • Tape measure : minimum 1 m of measuring length.

  • Test object : An object such as a cardboard box or similar that the robot can safely collide with. Recommended size: 200 mm high and 600 mm wide (approximating a cross-section of a human body lying on the ground).

Changing the speed

You must set up your robot to drive at the different monitoring case speeds. In the robot interface, use the joystick in Default Dashboard to drive the robot at different speeds. Adjust the slider to change the robot's driving speed.

Figure 3.40 The Default Dashboard in the robot interface

<image: "speed_control.png">

| Case | Joystick speed | Drive direction | | --- | --- | --- | | The following is a generic example where the monitoring cases use speeds a, b, c, and d for both reverse driving and forward driving. See the manual for your robot application for the specific Protective field sizes. | | | Case Joystick speed Drive direction 1 a - 0.05 m/s Reverse 2 b - 0.05 m/s Reverse and forward 3 a - 0.05 m/s Forward 4 c - 0.05 m/s Forward 5 d - 0.05 m/s Forward | Case | Joystick speed | Drive direction | 1 | a - 0.05 m/s | Reverse | 2 | b - 0.05 m/s | Reverse and forward | 3 | a - 0.05 m/s | Forward | 4 | c - 0.05 m/s | Forward | 5 | d - 0.05 m/s | Forward | | Case | Joystick speed | Drive direction | | 1 | a - 0.05 m/s | Reverse | | 2 | b - 0.05 m/s | Reverse and forward | | 3 | a - 0.05 m/s | Forward | | 4 | c - 0.05 m/s | Forward | | 5 | d - 0.05 m/s | Forward |

Method

The following two sections describe how to perform a linear brake test and pivot brake test.

Linear brake test

A linear brake test must be conducted to ensure that the length of the Protective fields of the robot are correctly configured for each monitoring case and the planned payload.

After driving the robot toward a test object and braking occurs, the distance d between the stopped robot and the test object should be measured and recorded for each brake test. Before conducting a linear brake test, a pass criterion for the test must be defined.

Pass criterion = acceptable distance d for the site (we recommend 215 mm as a starting point, or 65 mm if personnel wear safety shoes).

To conduct a linear brake test for forward and reverse driving, follow these steps:

  1. Place a static test object front and center relative to the driving path of the robot—see Figure 3.41.

  2. Set the joystick to the lowest speed, and push the joystick directly forward for forward driving (or directly backward for reverse driving) to drive the robot straight towards the test object.

  3. Once the robot has completed braking and come to a complete stop near the test object, measure and record the distance d from the part of the robot that is closest to the test object.

  4. Repeat steps 2–3 a total of five times for the selected joystick speed.

  5. Repeat steps 2–4 for each joystick speed.

Figure 3.41Linear brake test diagram

<image: "brake_test_linear.svg">

The test is considered passed when the distance d is equal to or greater than the pass criterion value. Likewise, the test is considered failed when the distance d is less than the pass criterion value. “P” for Pass or “F” for Fail should be recorded for each test in the test matrix.

Download an excel version of the brake test table template you can modify to your setup: Brake_test_template_table_v1.0.xlsx.

| | Forward driving speed (m/s) | Reverse driving speed (m/s) | | --- | --- | --- | | 0.1 | 0.3 | ... | | | | | -0.1 | -0.3 | ... | | | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | | Test 1 | | Result | | | | | | | | | | | | | | d (mm) | | | | | | | | | | | | | | Test 2 | | Result | | | | | | | | | | | | | | d (mm) | | | | | | | | | | | | | | Test 3 | | Result | | | | | | | | | | | | | | d (mm) | | | | | | | | | | | | | | Test 4 | | Result | | | | | | | | | | | | | | d (mm) | | | | | | | | | | | | | | Test 5 | | Result | | | | | | | | | | | | | | d (mm) | | | | | | | | | | | | |

Pivot brake test

The pivot brake test must be conducted to ensure that the width of the standstill Protective field for the robot is sufficient to prevent a collision when the robot is pivoting on its axis with maximum payload.

If you are using the default SICK configuration, the standstill Protective field corresponds to monitoring case 1 (0 to 0.1 m/s) for forward and reverse driving.

After pivoting the robot toward a test object and braking occurs, the distance p between the stopped robot and the test object should be measured and recorded for each brake test. Before conducting a pivot brake test, a pass criterion for the test must be defined.

Pass criterion = acceptable distance p for the site (we recommend 215 mm as a starting point, or 65 mm if personnel wear safety shoes).

Determine the distance S for object placement relative to the side of the robot.

Figure 3.42 Illustration of W and S

<image: "s_definition_txt_en.svg">

To conduct a pivot brake test to the left and right of the robot, follow these steps:

  1. Place a static test object a distance S to the left of the front-left corner of the robot (or to the right of the front-right corner of the robot). Make sure the object is placed just outside of the standstill Protective field so that the robot is not in Protective stop—see Figure 3.43.

  2. Positioned in front of the robot and using the joystick, push the joystick directly to the left for pivoting the robot in a clockwise direction (or directly to the right for pivoting the robot in a counterclockwise direction) toward the test object.

  3. Once the robot has completed braking and come to a complete stop near the test object, measure and record the distance p from the part of the robot that is closest to the test object.

  4. Repeat steps 2–3 a total of 5 times.

  5. Repeat steps 1–4 for pivoting the robot to the right toward a test object.

Figure 3.43Pivot brake test diagram

<image: "brake_test_pivot.svg">

The test is considered passed when the distance p is equal to or greater than the pass criterion value. Likewise, the test is considered failed when the distance p is less than the pass criterion value. “P” for Pass or “F” for Fail should be recorded for each test in the test matrix. Download an excel version of the brake test table template you can modify to your setup: Brake_test_template_table_v1.0.xlsx.

| | Left | Right | | --- | --- | --- | | Test 1 | | Result | | | | p (mm) | | | | Test 2 | | Result | | | | p (mm) | | | | Test 3 | | Result | | | | p (mm) | | | | Test 4 | | Result | | | | p (mm) | | | | Test 5 | | Result | | | | p (mm) | | |