Regbot motor parameters
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Motor parameters
The Regbot has a built-in estimator of motor parameters. This relies on a poorly designed motor current measurement and noisy velocity measurements.
These measurements can be repeated using the Regbot GUI. See User_interface#Motor_test. There is a tab called Wotor. Run the test a few times to get a sense of the variability in values. It can also be advantageous to warm up the motor lubrication by running a short mission before the test.
Measured values (Km, R, L)
These measurements were taken during maintenance in January 2026; not all values were recorded, but the list can serve as a guide when creating a simulated model of the robot.
The motor constant (Km) is estimated from the steady-state velocity, the input voltage, and the motor current and resistance. The uncertainty primarily arises from poor current measurement, but also from variation in the permanent magnet strength.
The motor resistance (R) is estimated from the peak current as the voltage is varied, and before the motor has changed velocity.
The inductance (L) is estimated from the time it takes to increase the current to steady-state and before the motor has changed velocity. The peak current is used as the steady-state. The current at two times is used to estimate the exponential rise in current, i.e., the time constant of the L/R circuit. The sample time used for these measurements is 0.3ms. This value may vary across motor generations but should be reasonably constant within them. The newer generation of motors typically has a motor constant (Km) of 0.012, where the older versions have a value closer to 0.01. Some motors appear to have a lower value; it could be due to a weaker permanent magnet.
ID Name K-left K-right R-left R-right L-left L-right (V/(rad/sec)) (Ohm) (Ohm) (Henry) (Henry) 1 Emma 0.0094 0.0096 2.4 7.8 5.6E-03 6.4E-03 2 Sofia 0.0096 0.0095 2.8 8.3 4.7E-03 7.0E-03 3 Ida 0.0105 0.0102 3.4 4.0 7.8E-03 3.6E-03 8 Ella 0.0111 0.0111 2.2 5.2 3.8E-03 3.7E-03 10 Karla 0.0128 0.0126 3.6 8.2 4.5E-03 15.7E-03 18 Agnes 0.0118 0.0116 3.2 6.3 6.1E-03 6.5E-03 19 Lily 0.0113 0.0110 3.5 4.8 4.9E-03 4.0E-03 25 Emilie 0.0095 0.0090 8.8 4.3 15.7E-03 3.2E-03 30 Rosa 0.0123 0.0122 2.9 7.6 5.9E-03 6.5E-03 31 Lea 0.0104 0.0105 3.6 5.5 6.0E-03 4.5E-03 32 Signe 0.0128 0.0120 3.0 7.8 5.1E-03 6.8E-03 33 Filippa 0.0097 0.0099 2.6 5.5 5.6E-03 4.3E-03 34 Julie 0.0114 0.0117 2.6 7.8 4.5E-03 8.7E-03 36 Liv 0.0130 0.0126 2.8 5.2 4.1E-03 2.9E-03 37 Vigga 0.0110 0.0111 3.2 9.5 4.5E-03 26.6E-03 38 Nanna 0.0105 0.0125 4.3 5.7 8.9E-03 4.4E-03 39 Naja 0.0103 0.0104 3.7 6.1 6.7E-03 3.9E-03 40 Alba 0.0122 0.0124 2.9 4.4 3.0E-03 2.6E-03 42 Aya 0.0120 0.0104 2.7 6.4 4.3E-03 6.6E-03 44 Luna 0.0113 0.0110 3.5 6.2 6.6E-03 4.8E-03 45 Malou 0.0122 0.0122 3.1 7.9 3.8E-03 6.2E-03 46 Esther 0.0110 0.0106 2.9 4.8 5.8E-03 3.9E-03 47 Celina 0.0105 0.0106 2.9 6.9 5.6E-03 5.7E-03 49 Andrea 0.0095 0.0095 3.9 4.4 11.7E-03 4.4E-03 50 Silje 0.0098 0.0098 2.2 6.5 3.6E-03 5.1E-03 52 Adriana 0.0091 0.0095 4.6 9.6 8.3E-03 9.0E-03 53 Dicte 0.0127 0.0121 3.5 4.5 14.7E-03 3.8E-03 54 Silke 0.0107 0.0099 2.6 7.1 5.5E-03 5.8E-03 56 Gry 0.0104 0.0113 2.7 6.5 4.4E-03 6.0E-03 57 Tania 0.0098 0.0103 3.3 6.4 6.8E-03 6.9E-03 58 Susanne 0.0096 0.0099 3.4 7.3 5.6E-03 6.6E-03 60 Birte 0.0100 0.0099 2.7 9.4 6.1E-03 7.0E-03 61 Dagmar 0.0116 0.0116 3.2 5.6 3.8E-03 3.3E-03 64 Molly 0.0108 0.0113 4.9 4.4 9.9E-03 3.9E-03 65 Ingrid 0.0112 0.0117 2.0 3.6 2.4E-03 2.0E-03 67 Nicolin 0.0104 0.0116 2.2 7.6 4.3E-03 5.9E-03 68 Tilde 0.0114 0.0110 2.2 4.0 4.1E-03 7.1E-03 69 Europa 0.0105 0.0096 2.5 3.8 4.8E-03 4.3E-03 70 Saga 0.0128 0.0127 2.5 5.4 3.5E-03 3.7E-03 72 Emilia 0.0100 0.0092 2.7 7.3 3.9E-03 6.2E-03 77 Alex 0.0118 0.0122 1.4 3.5 1.6E-03 2.1E-03 78 Melina 0.0120 0.0113 2.7 3.7 3.2E-03 2.1E-03 79 Amanda 0.0182 0.0119 2.2 3.2 6.0E-03 1.6E-03 80 Hannah 0.0115 0.0114 2.2 5.5 2.0E-03 3.0E-03 81 Jasmin 0.0117 0.0119 2.1 4.2 2.1E-03 2.3E-03 84 Cleo 0.0111 0.0112 2.3 5.6 2.0E-03 3.7E-03 85 Solvej 0.0114 0.0114 3.1 6.1 4.3E-03 3.9E-03 87 Ronja 0.0111 0.0114 2.5 6.0 2.7E-03 3.2E-03
Measured values (Friction and Inertia)
These measurements were taken during maintenance in January 2026; not all values were recorded, but the list can serve as a guide when creating a simulated model of the robot.
Dynamic or viscous friction (D) is calculated in a steady state by comparing the velocities and the current difference between the two velocities. Dynamic friction can vary among motors; it depends, e.g., on the lubrication, temperature, and commutator condition. The estimate is further hampered by the poor current measurement.
The moment of inertia (J) is estimated from the time required to reach steady-state velocity. The actual moment of inertia (J) will be equal across all motors with high accuracy. The variation in the estimate indicates a high measurement uncertainty.
ID Name D-left D-right J-left J-right % (Nm/(rad/sec)) (Nm/(rad/sec)) (Kgm^2) (Kgm^2) 1 Emma 1.2E-06 815.7E-09 1.3E-03 861.8E-06 2 Sofia 1.4E-06 1.4E-06 1.3E-03 863.2E-06 3 Ida 913.7E-09 2.1E-06 1.1E-03 1.9E-03 8 Ella 8.5E-06 8.5E-06 4.3E-03 4.0E-03 10 Karla 2.9E-06 2.8E-06 1.4E-03 1.2E-03 18 Agnes 5.5E-06 5.5E-06 1.5E-03 1.3E-03 19 Lily 1.0E-06 1.1E-06 1.2E-03 1.6E-03 25 Emilie 883.4E-09 2.1E-06 960.7E-06 3.7E-03 30 Rosa 17.4E-06 3.2E-06 4.8E-03 3.3E-03 31 Lea 1.5E-06 1.7E-06 2.6E-03 3.6E-03 32 Signe 7.3E-06 4.1E-06 4.2E-03 3.6E-03 33 Filippa 2.6E-06 2.9E-06 3.4E-03 3.4E-03 34 Julie 2.5E-06 2.5E-06 4.7E-03 3.1E-03 36 Liv 4.0E-06 4.5E-06 3.9E-03 5.0E-03 37 Vigga 2.3E-06 1.3E-06 3.7E-03 2.5E-03 38 Nanna 1.3E-06 1.2E-06 2.5E-03 4.2E-03 39 Naja 1.2E-06 1.7E-06 2.6E-03 3.4E-03 40 Alba 4.3E-06 4.5E-06 3.8E-03 4.9E-03 42 Aya 4.6E-06 1.6E-06 4.4E-03 3.0E-03 44 Luna 1.9E-06 2.5E-06 3.4E-03 3.9E-03 45 Malou 2.4E-03 3.0E-06 3.1E-03 3.1E-03 46 Esther 1.9E-06 2.4E-06 4.0E-03 4.0E-03 47 Celina 2.0E-06 1.6E-06 3.9E-03 3.2E-03 49 Andrea 1.8E-06 2.9E-06 2.1E-03 3.9E-03 50 Silje 2.7E-06 1.3E-06 4.2E-03 2.7E-03 52 Adriana 1.7E-06 1.6E-06 1.9E-03 1.7E-03 53 Dicte 3.4E-06 3.3E-06 3.4E-03 4.6E-03 54 Silke 3.4E-06 2.0E-06 3.7E-03 2.8E-03 56 Gry 2.5E-06 1.8E-06 3.7E-03 3.3E-03 57 Tania 1.4E-06 1.4E-06 2.9E-03 3.1E-03 58 Susanne 1.9E-06 1.6E-06 2.7E-03 2.6E-03 60 Birte 780.2E-09 726.3E-09 3.4E-03 2.0E-03 61 Dagmar 1.8E-06 1.7E-06 3.1E-03 3.4E-03 64 Molly 1.8E-06 3.7E-06 2.2E-03 4.4E-03 65 Ingrid 1.5E-06 2.4E-06 4.5E-03 5.9E-03 67 Nicoline 2.8E-06 1.5E-06 4.2E-03 2.9E-03 68 Tilde 2.3E-06 3.3E-06 4.5E-03 5.0E-03 69 Europa 2.6E-06 2.6E-06 4.0E-03 4.9E-03 70 Saga 4.4E-06 4.2E-06 4.3E-03 3.9E-03 72 Emilia 1.8E-06 1.9E-06 3.3E-03 2.4E-03 77 Alex 3.1E-06 2.6E-06 7.0E-03 8.1E-03 78 Melina 1.6E-06 8.0E-06 3.5E-03 5.1E-03 79 Amanda 4.0E-06 2.3E-06 11.4E-03 6.3E-03 80 Hannah 1.5E-06 1.2E-06 4.6E-03 3.5E-03 81 Jasmin 1.8E-06 1.9E-06 4.7E-03 5.0E-03 84 Cleo 1.6E-06 1.2E-06 4.3E-03 3.3E-03 85 Solvej 1.1E-06 1.4E-06 3.2E-03 3.3E-03 87 Ronja 1.8E-06 1.3E-06 4.2E-03 3.6E-03
